Phylanton N, the mixture of adducts of a-terpincne with 3-buten-2-one, was prepared by Dicls-lder reaction of a-erpinene with 3-uten-one in the presence of catalyst. This product which has woody and ambergris odors is a kind of ingredient with very good fragrance. The best reaction conditions are determined by discussing the effects of catalysts, reaction temperature, reaction time, catalyst amount and the ratio of a-erpinene to 3-buten-2-one. The catalyst L1 is used because of its good catalyst activity. The yield of Phylanton N is more than 82% at the best reaction condition. The quality of our product accords with the specification of Dragoco Company product by distillation of the reactive mixture.