Path-planning technology is an essential radiation protection measure to reduce radiation exposure to workers in nuclear emergencies. The terrain in the actual radiation environment is often diverse and also impact personnel movement speed differently. It is a multi-objective optimization problem for distance, dose, and terrain. However, there are only path-planning methods considering some of these factors. We creatively quantify the difference in terrain to movement speed and propose a path-planning method for Complex Terrain based on the A∗ algorithm (CTA) in the radiational environments. The CTA algorithm divides the influence of terrain on movement into accessible and inaccessible, and the reachable part quantifies the influence of terrain as velocity, which can give the minimum dose path in complex nuclear environments. Three simulation experiments confirm the method’s superiority. The simulation experiments show that the CTA algorithm works better in complex terrain than the traditional algorithm.