In order to investigate the optical properties and the stability of a diffuser panel used for on-board calibration for satellite optical sensors under space environments,some reflective properties including the Directional/Hemisphere Reflectance (DHR),Bidirectional Reflectance Factor (BRF)and the Bidirectional Reflectance Distribution Function(BRDF) were measured,and a series of environment simulation tests were performed.Experimental results show that the reflectances achieve 0.99 at VNIR,0.95 at SWIR;and the differences of the reflectances at VNIR are within 0.01;The variations of BRF(10-60°) and BRDF (0-60°) are less than 0.1 and 0.045,respectively,and the Lambertian property of the diffuser panel is independence on the spectral band and UV radiation.Moreover,the degradation of reflectance at 350 nm is within 3% after 120 h equivalent solar UV radiation and the atomic oxygen exposure or proton bombardment has little effect on the optical properties of the diffuser panel.As characterized by above,the diffuser panel has gotten through on-orbit level mechanical environment tests.For its high reflectance,spectral flatness,Lambertian characteristics and stability in orbit, the diffuser panel can satisfy the requirements for space applications.