Taking tomato variety‘Jinguan 58’as scion，‘Guozhen No.1’as rootstock，this study designed 4 treatments with different tomato seedling ages as 1 leaf stage，2 leaf stage，3 leaf stage and 4 leaf stage；and studied the effects of different seedling ages on tomato grafting．Through analyzing the difficulty degree of operation，activity changes of 2 enzymes POD and PAL，callus cells in grafted incision，plants growth situation after field planting，and survival rate of post grafting，etc.，the paper preliminarily determined that 2 and 3 leaf stages were the most suitable time for tomato seedling grafting．