The edible mushroom C. comatus easily take place a disease called “black cap”, so its fruitbody will rapidly decay, the consequence is a serious loss of production. For investigating the reasons, a few fungi was isolated from the rotten fruitbody, both the dual culture and aggressive experience were tested between the isolated fungi and shaggy cap mycelia or its buttons, one strain fungus called T. virens could both inhibit the growth of shaggy cap mycelia and invade its buttons, and the symptoms was very similar to that from the rotten fruitbody when the spore concentration was up to 1.8×10⁵cells/ml in soil, thus we can conclude that T. virens was the main pathogen inducible “black cap” disease. Carbendazim capable of inhibiting the mycelia and spores of the fungus T. virens was considered the best fungicides among thiophanate-methy, mancozeb and carbendazim.