Bacillus thuringiensis (Bt) is widely used in insecticides.Bt is a gram positive spomlation bacterium belonging to Bacillaceae family.It produces different insecticidal proteins like Cry toxin,Vip toxin,β-exotoxin and chitinase,etc.Bt insecticidal crysta1 proteins (ICPs) are not homologous to other known Vip protein and then act against lepidopteran,dipteran,coleoptenn and nematodeslarvae via a unique process.In this experiment,mod high-throughput sequencing technique and sequencing were used and the whole genome sequence of BtLTS290 was obtained.The results compared to the database of GenBank showed that there was a cry57 gene in the genome sequence of BtLTS290.A novel cry57 gene was cloned and named cry57Abl (accession number is KF638650) by Intational Nomenclature Committee ofBt Endotoxin.cry57Abl gene could be expressed with the molecular weight of 90 ku.Cry57Ab1 protein had no obvious activity against Spodoptera exigua and Helicoverpa armigera.And Cry57Ab1 protein had a slight insecticidal activity against Ostrinia facalis and Plutella xylostella.Furthermore,the domain Ⅱ of Cry57Ab1 and Cry1Bb were exchanged by overlapping extension PCR.SDS-PAGE showed that the molecular weight of Cry57Ab/1Bb/57Ab was about 90 ku.The insecticidal activity of Cry57Ab1 protein and Cry57Ab/1Bb/57Ab recombinant protein were determined.The results showed that the insecticidal activity of the recombinant protein to Spodoptera exigua and Helicoverpa armigera was very low,and the corrected mortality was less than 10％.The insecticidal activities against Ostriniafacalis and Plutella xylostella were reduced.The corrected mortality of Ostriniafacalis was 4.4％,and the corrected mortality rate for Plutella xylostella was 6.7％.Domain Ⅱ of cry toxin played a key role on affecting host specificity.