Abstract: Effects of toyocamycin against Rhizoctonia solani were tested by mycelial growth rate and pot experiment. Results indicated that toyocamycin strongly inhibited mycelial growth and sclerotium formation of R. solani, with EC₅₀ against mycelial growth at 1.67 mg·L^-1. The sclerotium formation of R. solani was entirely inhibited by toyocamycin at 2.20 mg·L^-1. After treatment for 14 d, the therapeutic effect of toyocamycin at 19.54 mg·L^-1 against R. solani in potted cucumber seedling was 71.91%, significantly higher than that of 1000-fold diluted hymexazol, while the protective effect was 51.06%, without significant difference from that of 1000-fold diluted hymexazol. The protective and therapeutic effects after treatment with 19.54 mg·L^-1 and 9.77 mg·L^-1 for 14 d and 21 d showed no significant difference.