Abstract: Chemical emasculation experiment were carried out in biclonal seed orchard of Chinese fir(Cunninghamia lanceolata) in Suichang County, Zhejiang Province from 1996 to 2000. The chemical emasculation with the compound of 45% paraquat and 10% glyphosate were commonly used at present. The results showed that:(1) Under the suitable prescriptions, the compound of 45% paraquat and 10% glyphosate is one of the inexpensive, easy and ideal chemicals of emasculation.(2) In this experiment, the suitable spraying time is 20 days before the male cone begin to dust. For the sake of safety, if the spraying begin after the formation and differentiation of male cone, but before its growth and development, i.e. before the flow of tree liquid(in dormancy), the effect will be better.(3) The optimal mixture ratio of 45% paraquat and 10% glyphosate is(8 g:15 mL)～(8 g:25 mL), diluting 80 times when using. It is better to spray 3 times.