NOVELTY - Preventing and controlling watermelon fusarium wilt, comprises (a) taking out stubble crop residues, carrying out soil tillage at 20-25 cm, adding an organic manure and chemical fertilizers, planting watermelon at the center at width of 110 cm once the soil temperature is above 15 degrees C, adding 45-50 g/m2 dazomet using an applicator, carrying out soil tillage, and adjusting soil moisture content at 20-30%; (b) covering the center of watermelon planting using a plastic film, covering soil to a width of 100 cm, and disinfecting; and (c) adding Trichoderma solid agents using applicator.    USE - The method is useful for preventing and controlling watermelon fusarium wilt using Trichoderma viride (all claimed).    ADVANTAGE - The method is environmental friendly, and has strong inhibition effect on growth of watermelon fusarium wilt.    DETAILED DESCRIPTION - Preventing and controlling watermelon fusarium wilt, comprises (a) taking out stubble crop residues, carrying out soil tillage at 20-25 cm, adding an organic manure and chemical fertilizers, planting watermelon at the center at width of 110 cm once the soil temperature is above 15 degrees C, uniformly adding 45-50 g/m2 dazomet using an applicator, carrying out soil tillage at 20-25 cm, and adjusting soil moisture content at 20-30%; (b) covering the center of watermelon planting using a plastic film, covering soil to a width of 100 cm, and burying plastic film edges into soil to a depth of 30 cm, and disinfecting for 12-20 days; and (c) planting the seedlings along the central line, cutting the plastic film to expose both sides, and ventilating for 3-4 days, and uniformly adding 45-60 g/m2 Trichoderma solid agents using applicator, carrying out soil tillage, planting watermelon seedlings, and covering plastic film around watermelon seedlings, where the content of the solid inoculant of Trichoderma in not less than 1x 109 colony-forming units (cfu)/g. An INDEPENDENT CLAIM is also included for use of Trichoderma viride in preventing and controlling watermelon fusarium wilt, has a preservation number of CGMCC NO. 9293.