Abstract: Fertility of F 1 and F 2 generation of the crosses among seven indica photo thermo sensitive genic male sterile (PTGMs) lines of four different sources was analyzed in the season of high temperature with long daylight in Guangzhou from 1993 to 1995.Results indicated that sterile lines N12S and N18S possessed two pairs of recessive alleles for male sterility . W7415S and 5460S,AnnongS 1, W7415S and N12S(N18S) were partially allelic ,meaning that they possessed one pair of allelomorphs. But the sterile genes of W6154S,Hengnong 1S were nonallelic to that of the other six of PTGMs ,5460S was nonallelic to the other five PTGMs except W7415S. Meanwhile, the differentiation from partial allelism to complete allelism, and the utilization of the photo thermo sensitive genic male sterile germplasm in hybrid rice breeding were also discussed in this paper.