Abstract: Effects of different topping positions on leaf senescence were studied using the muskmelon varieties of Honey World and Luhoutian No. 2 grown in solar greenhouse by analyzing the contents of soluble protein (Pr), chlorophyll (Chl) and malondialdehyde (MDA), and the activity of peroxidase (POD). The results indicated that the physiological activities of leaves (adjacent to fruits) for the plants topped at the 18th and 24th nodes were stronger than those topped at the 30th node within 7 days after pollination. The contents of Pr and Chl of the former were obviously higher than the later, and the MDA content and POD activity were lower than that. After 14 days of pollination, the topping at the 24th node retarded leaf senescence, and its effect was superior to those at the 18th and 30th nodes. After being topped, the changes of physiological indexes for leaves at different nodes further confirmed that the topping at the 24th node can retard the leaf senescence remarkably. To sum up, about the 24th node was the proper topping position, and it can be raised for the premature cultivar while it should be reduced for the serotinous cultivar.