The reaction condition of the preparation of a-erpincne from Chinese terpentine has been studied. The results show that in the presence of some catalysts, the yield of a-terpinene was affected by the reaction temperature and time period, the concentration and amount of the catalysts. At the best reaction condition in the presence of acidic catalyst (50℃, concentration acid 52%, H+ : terpentine = 0.3 : 1 (mol), 7 h), the content of a-terpinene in the reaction mixture is above 45% and the yield of a-tcrpincne is over 40%. On the effect of a cation resin, the yield of a-terpincnc is 33.5% at the suitable reaction condition.