The invention discloses a small-interference stability optimization method and device for an AC-DC hybrid system containing VSC-HVDC, and the method comprises the following steps: modeling an AC-DC power system to obtain a system dynamic model; acquiring related parameter sensitivity of a VSC-HVDC system under different DC transmission powers according to a system state matrix in the system dynamic model; determining whether the related parameter sensitivity of the VSC-HVDC system is a positive value or not: if yes, reducing the related parameter sensitivity of the VSC-HVDC system to increasethe oscillation damping ratio; if the related parameter sensitivity of the VSC-HVDC system is negative, increasing the related parameter sensitivity of the VSC-HVDC system to increase the oscillationdamping ratio, wherein the related parameters of the VSC-HVDC system include a converter station AD bus voltage of the VSC-HVDC system, converter station output reactive power of the VSC-HVDC system,and a converter station DC voltage of the VSC-HVDC system. According to the invention, the method can consider the influence of the state quantity of an Ac system in the AC-DC hybrid system on a flexible DC power transmission system, so that the accuracy of improving the small interference stability is improved.