The classification of heterotic groups is essential to maize breeding because knowledge of heterotic groups could be interest to both the combination of outstanding hybrids and the improvement of elite inbred lines. RFLP has provided a powerful tool to assign maize inbred lines into heterotic groups. In this investigation, 45 inbred lines, used widely in south and southwest China, were chosen for RFLP analysis, among which 4 lines came from American, representing different heterotic groups in U.S. corn belt. 54 RFLP core markers covering 10 chromosomes of maize were used. A total DNA of each sample was digested with EcoR I, BamH I and Hind 1. The procedure of RFLP was employed as described by a manual from maize RFLP lab at University of Missouri, Columbia. A total of 860 bands were detected among 45 inbred lines based on RFLP analysis, which were involved in 212 loci. Alleles at each locus ranged from 2 to 9 with an average of 4.06. In total, The 45 inbred lines were classified into 6 heterotic groups The classification of heterotic groups is essential to maize breeding because knowledge of heterotic groups could be interest to both the combination of outstanding hybrids and the improvement of elite inbred lines. RFLP has provided a power tool to assign maize inbred lines into heterotic groups. investigation, 45 inbred lines, used widely in south and southwest China, were chosen for RFLP analysis, among which 4 lines came from American, representing different heterotic groups in US corn belt. 54 RFLP core markers covering 10 chromosomes of maize were used. A total DNA of each sample was digested with EcoR I, BamH I and Hind 1. The procedure of RFLP was employed as described by a manual from maize RFLP lab at University of Missouri, Columbia. A total of 860 bands were detected among 45 inbred lines based on RFLP analysis, which were involved in 212 loci. Alleles at each locus ranged from 2 to 9 with an average of 4.06. In total, The 45 inbred lines were classified into 6 heterotic groups