To evaluate the effects of WEPO on the anti-asthma and on tension of tracheal smooth muscle.Methods:Asthmatic model was induced by ultrasonic atomization inhalation of histamine phosphate-acetylcholine chloride in guinea pig.The guinea pigs whose incubation period of asthma was less than 120s were selected and divided randomly they into 5 groups which were 1.25 g/kg，2.5 g/kg，5.0 g/kg of WEPO group，Ami 20 mg/kg group and control group.To evaluate anti-asthma the latent period induced asthma，the numbers of tracheal smooth muscle，the height of liquid in the capillary was recorded，and the difference of height of liquid between before and after treated by WEPO(Δh)and △h were computed.Results:The latent period induced asthma in low， medium and high-dose group were (108.2±19.1)s，(211.3±45.2)s and (226.9±41.5)s Respectively and these were lower than (59.5±10.8)s control group(P<0.05 or P<0.01).In WEPO medium and high-dose group the rate of asphyxia of animals were 40%and 30%respectively，and these were significantly lower than in control group(P<0.05).In low， medium and high dose group，Δh were (－5.02±1.03)，(－8.78±2.04)，(－10.32±2.24) respectively and these were significantly lower than(－0.5±0.21) in control group(P<0.05 or P<0.01).In low， medium and high -dose group △h were (2.24±1.01),(2.96±1.42),(3.21±1.49)，these were significantly lower than (0.71±0.45) in control group(P<0.05 or P<0.01).Conclusion:WEPO has significant anti-asthmatic effect and the effects are related with relaxation of tracheal smooth muscle and improve ventilation.