This paper studied the effects of 6 scion ages and 6 rootstock ages on graft survival rate，morphological index，chlorophyll content and root activity of seedlings grafted by hole insertion method using 2 factors completely randomized design．The result showed that the root activity firstly increased then decreased along with the increasing of rootstock age．The changes in leaf number，scion dry weight，graft survival rate，stem diameter，chlorophyll content of leaves were varied．With the increasing of scion age，graft survival rate，leaf number，stem diameter，scion dry weight，chlorophyll content of leaves and root activity were all increased then decreased．These watermelon seedlings with 9-13 days scion ages and 11-15 days rootstock ages had higher subordinative function value evaluated by method of membership function．These are the suitable ages of scion and rootstock for grafting by hole insertion method．