<p>Traditional landers typically encounter difficulties achieving stable landings because of the weak gravity and complex terrain of small celestial bodies. A multi-node lander with flexible connections can improve the stability of a small celestial body landing. However, this also poses new challenges, particularly for landing guidance in hazardous terrain. To address this problem, an equivalent simplified dynamic model of a multi-node flexible lander is first constructed, and its flat output is determined. Subsequently, a trajectory-planning method combining the flow and vector fields is designed to avoid collision, and the parameters of the vector field are optimized online according to the dynamic and obstacle constraints during the descent process to obtain a more suitable trajectory. Finally, the effectiveness of the proposed trajectory-planning method is verified through comparative simulations of landing and obstacle avoidance from the hover point to the landing area. This study offers new prospects for upcoming small celestial body landing missions in complex terrains.</p>