The space inflatable structure is a new construction technology and is the main demanding object in the future space activities. The inflatable structure is mainly made up of membrane; therefore, the maintenance of the structural surface accuracy is one of the most important problems. Wrinkling is the unique characteristic of the flexible membranes, and the wrinkles degrade the surface accuracy and the structural performance, so, the study on wrinkles in membrane structures is desirable and essential. In this paper, a prediction model of wrinkles is proposed, based on the buckling theory, and the wrinkles, including the wrinkle amplitude, wrinkle wavelength and the critical compressive stress, in a rectangular membrane subjected to in-plane horizontal shearing loads are predicted using the method proposed in the present paper. The predicted results show good agreement with our recent experiments and the reported data.