Display screen is an integral part of laser projection system. The surface roughness of screen directly affects speckle suppression based on angle diversity. The relation between speckle correlation and the surface roughness of measured screen is established by analyzing the speckle suppression method based on angle diversity. In the experiment, the incident angle is fixed to 1° and the angle increment is set to 0.0038°, which is a compromise between the sensitivities of surface roughness of the measured screen to those two factors. To avoid the effects of external perturbation and surface flatness on measured results, nine sub-regions are chosen in 5 cm×5 cm measured screen areas and measured results from these sub-regions are averaged, which effectively improves the measurement accuracy. The surface roughness for four screens determined by the proposed method are 235.80, 209.57, 132.24 and 137.60 μm, respectively, which provides a basis to design a projection display screen applied to effectively reduce laser speckle.