Abstract: The relationship between seed-producing number of Xinnong watermelon hybrid F1 and their weight and fruit-bearing number has been determined.The results showed that the correlative range between onemelon weight and its seed number during spring and autumn seasons is positively related from 0.4 to 4.8 kg and 0.4 to 3.8 kg respectively, belongs to the quadratic exponential equation.Within the range of 0.4 -3.0 kg one-melon weight, the seed-producing number increases linearly with the increase of melon weight in both two seed-producing seasons.The seed-producing number per plant is positively related to the increase of melon-bearing number.and belongs to the natural logarithm equation.But 100-seed weight and quality showed no significantly difference by the variance analysis.Thus, the measures for increasing seed-producing number in given area include two respects: (1) To increase watermelon number per plant; (2) To limit the watermelon weight below 3.0 kg.