The genetic diversity and correlation of twelve botanical characters were assessed in watermelon genetic resources in National Mid-term Genebank for Watermelon & Melon.The result of genetic diversity showed that：All botanical characters tested showed diversity indexes ranging from 1.02（fruit shape） to 2.37（1000-seed-weight） with an average of 1.70.The frequency distributions of botanical characters such as ground color of fruit surface, over color of fruit surface, flesh color, fruit weight, soluble solid content at center flesh, 1000-Seed-weight were dispersed. Variation coefficient of quantitative characters for average was 31.8. Variation range was 1-3 times greater than the average. The result of genetic correlation showed that：fruit shape and fruit ratio，flesh color and soluble solid content at center flesh，flesh color and 1000-Seed-weight，fruit rind thickness and fruit rind hardness was significantly related. 1000-seed-weight and soluble solid content at center flesh, fruit weight and fruit rind thickness, fruit weight and fruit rind hardness, over color of fruit surface and over color pattern of fruit surface was significantly related.