To control the two-dimensional galvanometer scanning system in light detection and ranging (LiDAR), the laser foot points can reach the detection width of 350 m or more, scanning grid point density in 1 spots/m² or more high pointing accuracy cone scan at a flight altitude of 1000 m and a flight speed of 200 km/h airborne LiDAR to sea bottom topography mapping. According to the characteristics of the two-dimensional galvanometer structure, this study uses the improved Bresenham algorithm to generate the trigger signal of the stepping motor in the control system and compensates for the beam lateral offset error caused by the two-dimensional galvanometer system, reducing the scan angle error to < 0.24 mrad. Simulation experiments demonstrate that the algorithm can cause the airborne LiDAR's two-dimensional galvanometer scanning system to achieve the conical scanning on the water surface with a laser foot point density of 1-5.59 spots/m² and scanning angle of 10°-60°, and the trigger signal derived by the algorithm is validated through experiments.