To identify the critical sterility-inducing temperature of dual purpose genic male sterile lines, Pei'ai 64S, Guangzhan 63S, Y58S, Xin'an S and Guangmo S were treated 5 days and 7 days with 22 ℃, 23 ℃ and 24 ℃ respectively. The results showed that low temperature treatment delayed heading dates and elongated the days from initial heading to ending heading. Sterile starting temperatures of all the 5 sterile lines were 24 ℃ except Peiai 64S, which was 23 ℃. In the process of identification of the critical sterility-inducing temperature, the confirmation of development stage of young panicles for inducing, the managements of materials after low temperature treatment and the correct sampling of individual panicles were important factors affecting the accuracy of identification.