Modeling and simulation of scan-imaging laser radar is an important research content in the field of signal processing and system design of laser radar. In order to improve the simulation efficiency without affecting the accuracy of the simulation simultaneously, a novel fast simulation algorithm is proposed. An inequation that can judge the intersection relations between the pixel and bins can be obtained by deriving the projection of their trajectories on the image plane. Then utilizing the time subdivision and approximate treatments to judge the potential intersection relations of pixel and bins. Finally, the goal of reducing the number of intersection operations can be achieved by testing all the potential relations and finding which of them is real intersection. The consequence of performing the new proposed simulation algorithm and the traditional algorithm in simulating 6 targets shows that they yield the same result, whereas the number of intersection operations of former is equivalent to only 1% of the latter.