Abstract: A niching genetic and ant colony optimization (NGACO) algorithm is proposed for the NP hard generalized assignment problem. NGACO is based on the combination of niching genetic algorithm and ant colony optimization algorithm to avoid local optima which often reside in the results of classical methods. Moreover, an intensive study on how to use this algorithm in GAP is made. Some experiments were made on weapon-target assignment problem (a typical application of GAP). Experiments' results are compared with those obtained by using other classical optimization algorithms. The results demonstrated that NGACO has high performance and short runtime in solving weapon-target assignment problem, and is viable for other NP-hard problems.