Abstract: The method of application of biocontrol microorganism is important for a successful biocontrol of crop diseases. An experiment was carried out to screen microorganisms and analyze their application methods in biocontrol of rice sheath blight. The T12 fungus screened was identified as Trichoderma asperellum. The applications of conidia powder (CP), organic fertilizer adsorbed mycelia (MA) and solid-state fermentation product (SS) of T. asperellum T12 were compared on effectiveness in biocontrol of sheath blight. SS exhibited best biocontrol efficacy, which was 89.5%. The cfus (colony forming unit) of T. asperellum adhering to sclerotia of Rhizoctonia solani in the soil was significantly higher in MA and SS treatments than in the control and CP treatments (P > 0.05). The MA and SS application methods enhanced the growth of T. asperellum along rice sheath. On the 60^th day, 100^th day and 130^th day after rice transplanting, T. asperellum population on leaf and sheath surfaces of rice indicated that the best and worst treatments were respectively CP and MA. R. solani population on leaf and sheath surface in the control treatment increased from 41 cfu·g^-1 to 272 cfu·g^-1 (P > 0.05), higher than that in the other treatments (P > 0.05). R. solani population in SS treatment was significantly lower than that in MA and CP treatments (P > 0.05). Compared with control treatment, all the three application methods induced higher enzyme activities of chitinase and β-1,3-glucanase (P > 0.05), while SS and MA induced longer disease resistance than CP. Therefore T. asperellum T12 application in solid-state fermentation production was considered the best application method for biocontrol of rice sheath blight.