[Objective]A large number of high-quality Bt transgenic sugarcane lines were obtained using transgenic technologies. This study aimed to explore the genetic background,genetic diversity,important traits and relationship between the heredity and phenotype of these transgenic sugarcane lines,thereby providing basis for further effective utilization and preservation of insect-resistant germplasm resources and improving breeding efficiency of insect-resistant sugarcane in China.[Method] By using six AFLP primers with high polymorphism,the genetic diversity of 13 Bt transgenic sugarcane lines and their donor varieties was analyzed. Growth assay and insect-resistance identification were carried out in a quarantine greenhouse with conventional methods. Evaluation of important economic traits was conducted in the field with conventional methods.[Result] The polymorphism rate was relatively low. Specifically,the polymorphism rate of the first group was 21. 00%,the polymorphism rate of the second group was 31. 80%,and the total polymorphism rate was 42. 50%. Cluster analysis showed that 13 Bt transgenic sugarcane lines and their donor varieties were divided into two categories,the genetic similarity coefficient between two categories was 0. 54. All the six materials in the first group were clustered into categoryⅠ,with genetic similarity of 0. 921; nine materials in the second group were clustered into category II,with genetic similarity of 0. 898. Bt transgenic sugarcane lines showed abundant phenotypic types and significant trait variations,and the economic traits were generally worse than donor varieties. The insect resistance of 13 Bt transgenic sugarcane lines was divided into five grades.[Conclusion] The first-generation Bt transgenic sugarcane lines have low genetic diversity,abundant trait variations,high insect resistance and generally poor economic traits,which can only be used as germplasm resources for hybridization. Introducing Bt gene into multiple donors will to some extent improve the genetic diversity of sugarcane germplasm resources,but the increasing rate is relatively low. It is preliminarily considered that the genetic diversity of insect-resistant sugarcane germplasm resources should be improved by continuous hybridization and backcrossing of Bt transgenic lines with high-quality parents,thus laying foundation for breeding high-quality insect-resistant sugarcane varieties. This study aimed to explore the genetic background, genetic diversity, important traits and relationship between the heredity and phenotype of these transgenic sugarcane lines, thereby providing basis for further effective utilization and preservation of insect-resistant germplasm resources and improving breeding efficiency of insect-resistant sugarcane in China. [Method] By using six AFLP primers with high polymorphism, the genetic diversity of 13 Bt transgenic sugarcane lines and their donor varieties was analyzed. Growth assay and insect-resistance identification were carried out in a quarantine greenhouse with conventional methods. Evaluation of important economic traits was conducted in the field with conventional methods. [Result] The polymorphism rate was relatively low. Specifically, the polymorphism rate of the first group was 21. 00%, the polymorphism rate of the secon d group was 31. 80%, and the total polymorphism rate was 42. 50%. Cluster analysis showed that 13 Bt transgenic sugarcane lines and their donor varieties were divided into two categories, the genetic similarity coefficient between two categories was 0. 54. All the six materials in the first group were clustered into category I, with genetic similarity of 0. 921; nine materials in the second group were clustered into category II, with genetic similarity of 0. 898. Bt transgenic sugarcane lines showed abundant phenotypic types and significant trait variations, and the economic traits were generally worse than donor varieties. [Conclusion] The first-generation Bt transgenic sugarcane lines have low genetic diversity, abundant trait variations, high insect resistance and generally poor economic traits, which can only be used as germplasm resources for hybridization. Introducing Bt gene into multiple donors will to some extent improve the genetic diversity of sugarcane germplasm resources, but the increasing diversity is relatively low. It is preliminarily considered that the genetic diversity of insect-resistant sugarcane germplasm resources should be improved by continuous hybridization and back crossrossing of Bt transgenic lines with high- quality parents, and laying foundation for breeding high-quality insect-resistant sugarcane varieties.