The invention relates to a reactive power compensation method for a doubly-fed wind power system. On the basis of a small-signal mathematical model of a static synchronous compensator, a designed sliding mode surface and a sliding mode controller designed on the basis of a reaching law arrival condition can effectively solve the problem of voltage fluctuation, caused by changes of a fan input power and a reactive power load, in an individual wind-electricity hybrid power system and the problem of uncertainty of parameters of a static synchronous compensator model; simulation is carried out through applying a step or random perturbation to the fan input power and the reactive power load in the individual wind-electricity hybrid power system; and the simulation result confirms the validity of the method provided by the invention.