Abstract: The current study was conducted to investigate the effects of chronic heat exposure on growth performance, meat quality and fat deposition in BeijingYou (BJY) chickens. One hundred and fortyfour 49dayold healthy BJY chickens (72 males and 72 females) with similar body weight (male (608.58±13.07)g, female (518.50±8.33)g) were randomly assigned into two treatments(hightemperature group(35±0.37)℃,optimaltemperature group(25±0.38)℃) with 6 replicates in each treatment and 6 birds in each replicate. The experiment lasted for 23 d. The growth performance (111,1222 and 122 d) and the carcass traits, meat quality and fat deposition on 12 and 23 d of BJY chickens were assayed. The result showed as followed；1) During 111 d, male and female weight gain was significantly decreased by heat exposure (P<0.01), but the ratio of feed to gain was not affected (P>0.05). During 1222 d, heat exposure depressed weight gain of male (P<0.01), and ratio of feed to gain of males increased by heat exposure (P<0.01); 2) Meat quality of males and females were not affected by heat treatment (P>0.05); 3) For males, abdominal, intramuscular and subcutaneous fat deposition, carcass proportion, and leg weight proportion were not affected by heat exposure on 12 d (P>0.05). Whereas, on 23 d, abdominal, intramuscular and subcutaneous fat deposition markedly decreased by heat exposure (P<0.01), but carcass proportion and leg weight proportion increased (P<0.05). For females, abdominal and intramuscular fat deposition decreased by heat exposure on 12 d (P<0.05). On 23 d, heat exposure decreased subcutaneous fat deposition (P<0.05), and abdominal and intramuscular fat deposition, carcass proportion, and leg weight proportion were not affected by heat treatment (P>0.05). These results suggest that 12 d heat exposure significantly depressed male and female weight gain. With the prolonged exposure time, weight gain of males decreased more severely, but females were not significantly affected, and fat deposition of males gradually decreased, but decreasing degree in females were relieved.