The invention relates to a preparation method of a rigid foam polyether polyester polyol, and belongs to the technical field of polyether polyol synthesis. According to the preparation method, a low molecular polyol is taken as a starting agent, under the effect of a catalyst, one segment epoxypropane is introduced for reaction; under negative pressure, suction of a polyester polyol is carried out, two segment epoxypropane is introduced for continuous reaction so as to obtain the rigid foam polyether polyester polyol. The preparation method is simple and convenient; the rigid foam polyether polyester polyol is moderate in viscosity, and excellent in compatibility with a foaming agent; and further prepared foam is excellent in toughness, and high in strength and size stability.