The genetic diversities of 12 weedy rices,34 cultivated rices and 36 wild rices were investigated by using 30 pairs of SSR primers,121 polymorphic bands were found,each SSR loci has 2-6 alleles,with an average number of 4.03.The genetic diversity index of weedy rice，cultivated rice and wild rice was 0.288 2、0.351 5 and 0.489 9,respectively.The average alleles of each loci were 2.1,2.27 and 3.53,respectively.This indicated that the genetic diversity of weedy rice was lower than that of cultivated rice and wild rice.The genetic distance between weedy rice and cultivated rice (0.049 4) was smaller significantly than that between weedy rice and wild rice,suggesting that the genetic relationship between weedy rice and cultivated rice was relatively closer and that weedy rice was probably degenerated atavisticly from cultivated rice.