Single pixel detection technology can realize two-dimensional imaging of object reflectivity or transmittance, but the imaging results will be affected by the incident angle of the illumination light, the shape of the object surface and the spatial orientation of the detector surface. The research shows that the modulation effect of these factors can be eliminated by the design of spatial non-uniform illumination. Therefore, a new single pixel imaging method is proposed in this paper. In order to enhance the image contrast and improve the image quality, the method reconstructs the spectrum of the imaging object by projecting two-dimensional cosine gray fringes with spatial modulated amplitude. The surface reflectance of the object is imaged, and the experimental results are consistent with the theoretical analysis, which verifies the effectiveness and feasibility of the method.