针对于避碰决策问题对算法时效性和轨迹分布性的要求，改进一种基于多目标优化算法NSGA-Ⅱ (non-dominated sorting in genetic algorithm Ⅱ).采用按需分层策略和考虑父代支配信息的算数交叉算子策略，降低了算法的时间复杂度，加快了收敛速度；提出动态分布适应度策略，控制了帕累托集在目标空间的分布.在此基础上，分别建立决策方案的安全性和经济性目标函数以及驾驶员对决策安全性的偏好函数，通过改进NSGA-Ⅱ对避碰决策方案寻优.试验结果表明，改进NSGA-Ⅱ的收敛速度和分布性有所提升，证明了改进算法的有效性和优越性；在构建的四种船舶会遇场景下，算法均能寻得多个兼顾安全性和经济性的避碰决策方案，为驾驶员避碰决策提供参考.

Aiming at the requirements of time effectiveness and trajectory distribution of collision avoidance decision-making problem, a non-dominated sorting in genetic algorithm Ⅱ(NSGAⅡ) based on multi-objective optimization algorithm was improved. The ondemand layering strategy and the arithmetic crossover operator strategy considering the parental domination information were adopted to reduce the time complexity of the algorithm and speed up the convergence. A dynamic distributed fitness strategy was proposed to control the distribution of Pareto sets in target space. On this basis, the safety and economy objective functions of the decision-making scheme and the driver’s preference function for decision-making safety were established respectively, and the collision avoidance decision-making scheme was optimized by improving NSGAⅡ. The experimental results show that the convergence speed and distribution of the improved NSGAⅡ are improved, which proves the effectiveness and superiority of the improved algorithm. Under the four types of ship encounter scenarios constructed, the algorithm can find multiple collision avoidance decision-making schemes that take into account both safety and economy, which provide reference for the driver’s collision avoidance decision-making.