In this study,analyses of phenotypic characters,SSR molecular markers and pedigrees were done to study the genetic diversity in 186 maize hybrids that were tested in regional trials in Sichuan and Southwest China.The results showed that there were differences in the variation coefficients of different characteristics,but all of the variation coefficients changed within a narrow range.Sixty pairs of simple sequence repeat (SSR) primer distributed on the ten chromosomes of maize produced stable amplified bands and 608 alleles were detected among the hybrids.The average number of alleles per locus was 10.1 ranging from 3 to 23.The values of polymorphism information content (PIC) for each SSR locus varied from 0.5179 to 0.9256 with an average of 0.7826.The genetic similarities of SSR marker patte among the 186 hybrids ranged from 0.6067 to 0.9162,with an average of 0.7722.There were 16499 pairs of genetic similarity,in which 96.9% were 0.70000 to 0.9256.The cluster analysis showed that the hybrids could be classified into ten clusters,with 88.2% of the hybrids included in Cluster 4,Cluster 8 and Cluster 10.The analysis of pedigree sources of 51 hybrids showed that 36 hybrids had close genetic relationships with the hybrids developed by the Pioneer Company in the late 1980s and early 1990s in the United States,such as Y78599,Y7865 and Y78698,accounting for 70.58%.Meanwhile,13 hybrids had close genetic relationships with Y78599,accounting for 8.66%.The genetic similarities of SSR marker patte among the 51 hybrids ranged from 0.66192 to 0.8799,with an average of 0.7686.There were 1196 pairs of genetic similarity ranged between 0.7000 to 0.8796,accounting for 93.80% of all the genetic similarity pairs.The cluster analysis showed that 88.2% of the 51 hybrids were in Cluster 4,Cluster 8 and Cluster 10,which indicated that similarity was high and genetic diversity narrow among the 186 hybrids.This showed that it is necessary to broaden the genetic basis of breeding germplasm in maize.