The olfactory behavior of Trichogramma dendrolimi Matsumura to nine pine needles volatiles were investigated with Y-tube olfactometer, four volatiles were identified could affect the olfactory behavior of T.dendrolimi,they were α-pinene,β-pinene,limonene and α-terpineol acetate,but it should be noted that α-pinene and β-pinene have a most significant effect. Bioassays to parasitic behavior of T.dendrolimi were conducted in laboratory,we mixed different compounds by these four or three volatiles to compare single components to investigate the percentage of parasitism,the results showed that both of them could affect the percentage of parasitism significantly,and this result also same as the conclusion of olfactory behavior experiment basically.However,compounds had not caused highest percentage of parasitism compared single components,this may suggested some single components play a dominant role in parasitic behavior of T.dendrolimi.