To address the drawback of traditional painting trajectory planning algorithm requiring extensive searching for nearest point pairs，a initial trajectory point extraction algorithm based on the point cloud thin-slicing technology was proposed.This algorithm determined slice thickness by calcula-ting the density of the point cloud model and designated points on the slice as initial trajectory points， thus improving operational efficiency by avoiding point pair searches. To tackle issues such as insufficient trajectory precision and excessive curvature caused by traditional linear interpolation algorithm， a trajectory fitting algorithm was introduced. This algorithm firstly maped trajectory points in three-dimensional space to a two-dimensional coordinate system and utilized the isolation forest algorithm to eliminate outlier trajectory points，followed by combining curve fitting methods for trajectory planning. Experimental results demonstrate that the trajectories planned by this algorithm exhibit higher precision and smoothness， while also enhancing the overall efficiency of the algorithm.