Tomato cv.L402 was used as plant material.Resistance to gray mold and activities of defensive enzymes were investigated after sprayed Ca²⁺ or its antagonist on tomato.The results showed that:(1)Resistance to gray mold were improved significantly for induced and uninduced leaves in tomato treated with SA.Induced resistance was farther enhanced by Ca²⁺ but restrained badly by chelator as EGTA or the plasmalemma Ca²⁺ channel blocker as LaCl₃.(2)Activities of PAL,PPO and POD in induced and uninduced leaves also rose after treated the plant with SA.This response was promoted by exterior Ca²⁺ and suppressed by the inhibitor of Ca²⁺ such as EGTA and La³⁺ in a general way.(3)Activities of CAT and SOD induced by SA were not regulated by Ca²⁺ or inhibitor of Ca²⁺.Consequently,modulating of calcium on the induced resistance to tomato gray mold by SA may has relations with the activities of defensive enzymes such as PAL,PPO and POD in tomato leaves.