Abstract: Temperature-humidity index (THI), temperature, relative humidity (RH) of chicken house in summer and autumn were investigated for discussing the effect of thermal environment on the incidence of breast blister in broilers. The results showed that average THI, temperature, RH in chicken house were respectively higher in summer than in autumn. They were 4.3, 7.3℃ and 13% higher in summer than in autumn especially when the broilers were six weeks old. Meanwhile, the incidence of breast blister in broilers was lower in summer than in autumn and the incidences of breast blister in broilers in summer were 21.56% and 40.22% lower than in autumn when the broilers were five and six weeks old, respectively. Total Anti-Oxidative Capability(T-AOC) in serum of broilers was significantly higher in summer than in autumn, but Malondiadehyde(MDA) content in serum of broilers was higher in autumn than in summer (P＜0.05). Therefore, the incidence of breast blister in broilers is lower in summer than in autumn, which maybe related with the improvement of anti-oxidative capability.