In recent years, facility cultivation in watermelon has become one of the main ways in China, and dwarf germplasm resources have been of interest considering their application for their unique advantages in facility cultivation. Dwarf is one important agronomic trait in modulating plant architecture, and dwarf watermelon varieties are adaptable for high-density planting, mechanizing management and pest control, which can effectively reduce costs and meet the current needs of simplified watermelon cultivation. In this study, 14 dwarf germplasms, which were collected from domestic and foreign countries, were subjected for self-pollination with several generations to obtain homozygous inbred lines. Fourteen dwarf germplasms were subjected for diallel crosses, and F1 hybrids and derived F2 populations were analyzed for plant architecture related agronomic traits. Based on allelic tests for 14 dwarf germplasms, two types (class-I and class-II) on the dwarf phenotype were observed. The dwarf trait in class-I mutants d1, d2, d3 and d6 was controlled by the same recessive gene Cldw1, while the dwarf trait in class-mutants was controlled by another recessive gene Cldf. The F1 hybrid derived from inter-crosses between two classes were observed with long vine, and the segregation ratio of the vine type in F2 population was 9:3:3:1, thus confirming that the dwarf trait in two types of mutants were controlled by two different recessive genes. The analysis of different dwarf germplasm mutants in this study provided better understanding of watermelon dwarf resources, which has implication in breeding for new watermelon dwarf varieties.