Abstract: Inhibitory effect of Chinese herb extracts Polygonum cuspidatum，phellodendron Chinese schneid，Magnolia officinalis，Usnea longissima Ach. were determined by the growth rates of mycelium of Monilinia fructicola in vitro. By line regression，50% of Effective Concentration (EC50) of Chinese herb extracts were 133.8μg/ml, 40.6μg/ml, 90.6μg/ml and 3.4μg/ml respectively. According to EC50，the five ratios were determined by the evidence of six equal-part points of additive action line, and synergism was judged by the method of co-toxicity factor. The result showed that the plant extracts of phellodendron Chinese schneid and Usnea longissima Ach. with combined ratio of 8:1were the best mixtures for controlling M. fructicola.