Abstract: This study was based on the primary screening of biocontrol actinomycetes against Fusarium oxysporium f. sp. niveum, then combined 3 strains (153, SC11 and SF6) into a multi-complex mixture, in order to improve the biocontrol effect on watermelon wilt disease. Actinomycetes strains with antagonistic activity in vitro were screened through petri dish test and pot examination. Three of them were mixed into a multi-complex to explore the biocontrol efficacy on watermelon wilt disease and the growth promotion on watermelon seedlings. Three single strains including SC11, 153, SF6 and the combined strain had inhibiting effect on F. oxysporium f. sp. niveum, the control efficacy was 25.87%, 20.61%, 16.72% and 47.50%, respectively, while the combined strain had the most remarkable effect, significantly higher than that of the single strain. On the other hand, the effect on the plant growth by the strains showed significant promoting, the increase of the fresh weight of plant by them were 99.26%, 124.44%, 144.44% and 162.22%, respectively. The increase of plant height, leaf area and chlorophyll content by the combined strain was 84.93%, 35.60% and 226.83%, respectively. The efficacy was remarkably higher than single agent. Regardless of the prevention or promoting aspects, the effect of the combined strain was the most ideal. The combined actinomycetes mixture had an improved biocontrol efficacy and growth promotion than the single strains; the traits could be achieved through the synergy of complementary advantages, and make the full use of their biocontrol effects.