Based on the internal structure of the circular scanning airborne laser bathymetry system coastal zone mapping and imaging lidar (CZMIL), the vector equations of laser in the prism, atmosphere and water are deduced and rectified to remove the mounting error of the prism, scanner and laser. With the vector equations and the attitude and location data provided by global position system/inertial navigation system, the laser point positioning model is deduced in the mapping coordinates. The intersection of laser line and sea surface is simulated depending on the mathematical principles of line and plane intersection. Combined with the direction vector of laser line in the water got by the refraction principle and the sea floor plane mathematical equation, the location of the laser points are simulated. Finally the influences of the plane attitude and height on the point clouds distribution are discussed deeply when the boresight misalignments are existed, which are meaningful to the calibration of system error and the correction of point clouds location for the circular scanning airborne laser bathymetry system.