Abstract: The effect of Zafirlukast on pulmonary hypertension (PH) induced by low ambient temperature in broiler chickens was investigated. Sixty male 17-day-old broiler chickens were randomly divided into three groups: normal ambient temperature group (NT,22~23 ℃), low ambient temperature group (LT, 9~11 ℃) and Zafirlukast group in low ambient temperature (ZLT, 9~11 ℃). At 31, 38 days of age, 7 birds were randomly taken from each group for measuring the pulmonary artery pressure by right cardiac catheter and femoral artery pressure (FAP) by directly measured methods. The ascites heart index (right ventricular weight/total heart weight，AHI) and the packed cell volume (PCV) was measured too. The results showed: (1) At 31 days of age, the pulmonary artery systolic pressure of ZLT was significantly higher than that of LT and NT(P＜0.05), and at 38 days the pulmonary artery diastolic pressure of ZLT was significantly higher than that of NT (P＜0.05). (2) The PCV of ZLT was significantly greater than that of LT (P＜0.05) at 31，38 days. (3) The AHI of ZLT was significantly greater than that of LT (P＜0.05) at 31 days. (4) The FAP of all groups were not significantly different (P＞0.05). These data indicate that Zafirlukast promote the development of PHS induced by low ambient temperature in broiler chickens.