This study aims to investigate the effect of farnesol， a kind of quorum sensing molecule， on the yield of triterpenoids and betulinic acid in the submerged fermentation of Inonotus obliquus. Microplate reader and HPLC were the main detection methods. The results of this study showed that with the increase of the addition of farnesol， the biomass of the fungus gradually decreased， that is， the addition of farnesol inhibited the growth of the cells. The triterpenoids in the mycelia， triterpenoids and betulinic acid in the fermentation broth increased with the increase of the addition of farnesol， all of which increased first and then decreased. For the three indexes， the optimum additions of farnesol were 150 μmol/L， 50 μmol/L and 100 μmol/L respectively. The content of betulinic acid in the mycelia increased with the increase of the addition of farnesol. This study indicated that the farnesol of appropriate addition can promote the content of triterpenoids in the mycelia of Inonotus obliquus and the fermentation broth as well as the content of betulinic acid in the fermentation broth.