In vitro detection method for sensitivity of Magnaporthe grisea to tricyclazole was studied and the potential resistance risk of M. grisea to tricyclazole was also assessed. Both EC50 of hyphal melanization (EC50 -H) and minimal inhibitory concentration of melanization in appressoria (MIC-A) by the inhibitor tricyclazole showed positive correlation to the EC50 of tricyclazole against blast disease tested in vivo, with relative co-efficiency (R2) of 0.8995 and 0.8244, respectively. However, the stability and reproducibility of EC50 -H were better than those of MIC-A, suggesting that it could be used to detect the sensitivity of M. grisea to tricyclazole in vitro. Tricyclazole sensitivity of the progenies derived from single spores of the most sensitive isolate DY2 and the least sensitive isolate GY6 detected in sensitivity monitoring study in year 2000 was not stable, with mean EC 50 values of 4.4968 μg/mL and 5.4010 μg/mL, respectively, indicating that the difference in EC50 between DY2 and GY6 was possibly not caused by resistance variation. EC 50 of GY6 did not significantly increase when continuously selected for twenty generations under the selection pressure of tricyclazole in vivo. However, the sensitivity of DY2 was decreased by 10-fold after selected for twenty generations. These results suggested that tricyclazole was still at low resistance risk for M. grisea in China.