Abstract: To understand stigma exsertion characters of photo-thermo sensitive genic male sterile lines（ PTGMS lines），the effects of“ 920” on stigma exsertion of 4 PTGMS lines were studied by spraying with“ 920”or not in the natural field conditions. The results showed that under natural conditions the stigma exsertion rates of the 4 PTGMS lines were at a high level between 79.8%~87.1% and the line with highest stigma exsertion rate was GD-7S，and most of the stigma exsertion were unilateral. The totalstigma exsertion rates of the PTGMS（except GD-7S） were all increased by spraying with“ 920”， especially for the unilateral stigma exsertion. For the bilateral stigma exsertion rates，the responses of the different PTGMS lines to“ 920” were different. The line with largest increase of stigma exsertion rate and best response to“ 920” was Xing86S. It could be seen that“ 920” could increase the stigma exsetion rates of the PTGMS lines in this study，especially the unilateral stigma exsertion rate.