Watermelon variety of Zaojia No.3 (8424) was selected and swelling fertilizer was used every 5 days after watermelon pollination, and the effects of swelling fertilizer on watermelon yield and quality were studied. The results showed that watermelon swelling fertilizer was supplied at proper time can promote the growth of watermelon, increase the yield of watermelon significantly, increase the weight of single fruit and sugar content of watermelon, improve the quality of watermelon. The appropriate time of swelling fertilizer for Zaojia No.3 (8424) was on the 13rd or 14th day after watermelon pollination.