Abstract: In order to overcome the problems of unreasonable flight parameters and poor point cloud data quality caused by the complex flight environment of UAVs in forests as well as diversified operations and difficulty in evaluating the quality of point cloud data, a method of setting flight parameters for UAV forest environment based on simultaneous localization and mapping was proposed. Firstly, the method constructed the forest point cloud data collected using 3 D LiDAR. Secondly, the quality of the point cloud data was evaluated by comparing and analyzing the mapping trajectory and the GNSS-RTK data trajectory. Finally, the optimal flight altitude and speed parameters of the UAV were set according to its root mean square error. The analysis results showed that when the flight speed was fixed, the root mean square error of the flight path of the airborne lidar was positively correlated with the flight height. When the flight altitude was fixed, the root mean square error of the airborne LiDAR flight trajectory was positively correlated with the flight speed. In the forest with an average height of 6-7 m and a length of 100 m, optimal flying height of the UAV was 12 m, optimal flying speed was 2 m/s, and root mean square error was 1.262 m. This method meets the needs of evaluating the quality of point cloud data, and provides theoretical support for the setting of UAV flight parameters in forest environment.