Abstract: The effects of calcium on synthesis of lignin induced by chemical elicitors in tomato were investigated in this study. The 3rd leaves were smeared with chemical elicitors: salicylic acid(SA), Methyl jasmonate(MeJA), -aminobutyric acid(BABA) and gentisic acid(GA) separately at the sixleaf stage of tomato. After the third leaves dried under room temperature, all the tomato plants were sprayed with CaCl2, distilled water, EGTA and LaCl3 in turn. The contents of lignin in the third leaves(induced) and the fifth leaves(un-induced) were determined in 0, 1, 2, 3 and 5 days after treatments. The results show that: (1) The lignin content in both the induced leaves and un-induced leaves increased after treated with chemical elicitors. (2) The lignin synthesis in treated tomato leaves were further promoted by exterior Ca2+, but inhibited by Ca2+ chelator EGTA and the plasmalemma Ca2+ channel blocker La3 + in different levels. These results indicated that Ca2+ play a positive regulation role in synthesis of lignin in tomato leaves induced by the above four chemical elicitors.