A new nor-labdane-type diterpene, 15-nor-labda-8(17),12E-dien-13,19-dienoic acid (1), along with five known diterpenes, 15-nor-14-oxolabda-8(17),12E-dien-19-oic acid (2), trans-communic acid (3), sandaracopimaric acid (4), dehydroabietic acid (5), and abieta-8,11,13-triene-15,18-diol (6), was isolated from the cones of Pinus luchuensis. The structure of 1 was established by chemical and spectroscopic methods. Among these isolates, compounds 2, 4, and 6 showed potent inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol 13-acetate.