A new thermo-photo-sensitive wheat male sterile line BNS has features of thorough infertility and stable fertility transition and has important value in wheat heterosis researches . To study the temperature and endogenous hormone contents related to fertility transition at different development stages, BNS was designed to sow at five sowing dates in autumn and spring. The contents of heteroauxin (IAA), abscisic acid (ABA), gibberellin (GA3) and zeatin riboside (ZR) were detected by enzyme-linked immunosorbent assay (ELISA) to analyze the dynamic changes of endogenous phytohormones in ears of BNS male sterility and fertility at different development stages. The results showed that BNS was sterile at normal sowing date in autumn but fertile in early sowing in spring in Guanzhong area of shaanxi province. The sensitive fertility stages of BNS were uninucleate and trinucleate stages and the critical temperature of fertility alteration was 15.35℃ and 18.64℃ respectively. At uninucleate stage, the content of IAA, GA3 and ZR in sterility BNS were lower 21.9%、33.6%、30.2% respectively than those in fertility BNS, but those of ABA higher 23.4%. Moreover, at trinucleate stage, the contents of ABA and ZR in sterility were higher 59.7% and 31.4% than those in fertility one, but those of GA3 lower 44.0%. Furthermore, the imbalanced ratios of IAA/GA3, ABA/GA3 and IAA/ABA in BNS sterility had harmful effect on anther development of anthers and induced their sterility.