Abstract: Exploitation and development new thermo and /or photoperiod sensitive male sterile materials will promote the theoretical research on the development of male gametophyte and give more approach for utility of the heterosis of rapeseed. In the present paper, the development and primary characterization of a new thermo-sensitive male-sterile line 373S in Brassica napus L. was reported. A chimerically male sterile rapeseed (Brassica napus L.) was found in the open-pollinated family from a spontaneous male sterile population. After successive selfing from this chimerically male sterile plant, an environment-sensitive male-sterile line 373S was bred. The influence of ecological factors on the male fertility was analyzed based on the data from cultivation experiment conducted in field and under controlled conditions. Atmospheric temperature 2-9 days prior to blooming had a predominate effect on the male fertility but the effect of daylength on it was not notable. The sensitive stage was further narrowed at the time when the bud was 2-3mm long (meiotic to uni-nucleic stage of microspore development). Therefore, 373S was characterized as a thermo-sensitive male sterile line and would become male sterile at higher temperature but render fertile at lower temperature. The F1 generations of the crosses of 373S with various varieties was observed to be 100% male fertile, and in the F2 generations, 7.1-14.6% plants was thermo-sensitive male sterile. The accurately characterization of the reaction to ecological factors, improvement of the agronomic traits and quality of 373S, search of the suitable region for hybrid production was under way.