Through analysis to the firepower assignment progress in air-to-ship attack, the air-to-ship firepower assignment model is established with the largest destroying effectiveness against main targets and the least time difference of arrival as the object function, and the limitation of the total number of the air-to-ship firepower, the limit of assigned amount for a single target, and the total length of anti-ship missile route planning as the constraint conditions. The model is solved by using Non-dominated Sorting Genetic Algorithm (NSGA-II). The feasible solution set of the model is obtained by designing of the algorithm and programming of Matlab. The result of the simulation analysis verifies that the model is feasible, and the calculation results can provide an accurate and reliable firepower assignment decision support for commanders.