Abstract: The effect of Ca²⁺ channel of mast cells (MC) on the development of pulmonary hypertension syndrome (PHS) was investigated in broiler chickens. The birds with PHS were induced by low ambient temperature. The pulmonary artery pressure was measured using right cardiac catheter. MC were stained with Alicience blue. Histamine was shown using immunohistochemistry. The deposit of Ca²⁺ was observed in MC by transmission electron micrograph. The results showed: (1) The Ca²⁺ channel blocking agent (verapamil) can decrease the pulmonary artery systolic pressure and pulmonary artery diastolic pressure significantly. (2) Verapamil decreased the right ventricular pressure and ascites heart index（P＜0.05）. (3) Verapamil promoted the number of MC in peripheral pulmonary blood vessel walls and right ventricle（P＜0.05）, and markedly decreased（P＜0.05） the ratio of degranulation of MC. (4) Verapamil increased the number of histamine positive cells in the lung（P＜0.05）. (5) Intracellular Ca²⁺ was increased significantly in degraunlated MC. These results suggested that verapamil inhibited the degranulation of MC and releasing mediators to prevent the development of the PHS.