Synchronous scanning underwater laser imaging is one of the advanced underwater imaging techniques which can effectively reduce water backscatter.A highly collimated laser beam is used to illuminate the underwater object,and the transverse FOV is expanded through synchronous scanning together with longitudinal motion of the platform,thus the 2-dimensional gray image is formed.A theoretical model for one dimensional target reflectivity was established,and the quantitative effect of laser divergence angle and sampling angle on angular resolution of synchronous scanning underwater laser imaging system was analyzed.The computational results show that the angular resolution of underwater laser imaging system can reach 0.6 δ when laser divergence angle being δ and the contrast ratio attenuation is not less than 0.2 times that of original target.