Object To determine the variety of aconitine and tetrandrin in decocting Radix Aconiti and Radix Stephaniae Tetrandrae separately and compatibly, and explore the mechanism of synergy between above two decocted herbs. Methods TLCS was used to determine the contents of aconitine and tetrandrin in separate decoctions and compatible decoction, respectively. Results The contents of both aconitine and tetrandrin were less in compatible decoction than in separate ones. Conclusion A scientific basis is provided by the compatible decoction of the two herbs for more effective and attenuate use.