Abstract: The techniques of applying tricyclazole aganist rice blast (caused by Pyricularia grisea )and factors decreasing control effects were studied. Notable effects were obtained by foliar spraying and root-soaking with tricyclazole controlling rice blast, and root-soaking was more effective. The high control effect could last as long as 10 days after leaf-spraying or root-soaking of tricyclazole. The second treatment with foliar spraying three days after the first treatment could increase and elongate control effects. The control effect was 81.3% sprayed before Pyricularia grisea invaded, but the control effect was only 35.6% treated after P. grisea invaded. If leaves of rice seedling were damaged, tricyclazole had no any control effect. If it rains 1 h after tricyclazole treatment, control effect may be decreased. While it rains after 3 h, there was not any influence on the control effect of the fungicide.