The present invention belongs to the field of medicine technology, and discloses a resveratrol derivative, its preparation method and application. The invention uses 3, 5-dialkoxyl-4'-hydroxydiphenylethene and P-hydroxybenzaldehyde as raw material and adopts a certain preparation process to prepare the invented compound resveratrol derivative. The medicinal alkali and medicinal salt have good effect for preventing and curing tumor, angiocardiopathy and inflammation diseases. The activity of the medicinal salt is obviously stronger than the resveratrol and the pterostilbene, and the medicinal salt is capable of improving the stability of the resveratrol and the pterostilbene, and can improve the kinetic parameters of the resveratrol and the pterostilbene. (R1 and R2 are methyl or ethyl or propyl group; n is 1 to 4; NR3R4 is common amine, for example dimethylamine, diethylamine, dipropyl amine, diisopropylamine, nafoxidine, piperidine, morpholine or substituted piperazine).