In the purpose of estimating the impact location of loose parts quickly and accurately in nuclear power plant prime circuit, a locating method based on two-dimensional optimization is proposed. Loose part location analysis model, which converts the locating problem into an optimization one, is established according to the position relationship between the sensors and the impact point. Then the location can be estimated by solving the optimization problem using Genetic Algorithm. The locating accuracy is improved as the error of wave velocity measurement is avoided in the proposed method. To verify the validity, the proposed method, the triangle method and the scanning method are used to process the simulation experiment data respectively. Comparison of locating error and time costing prove that the proposed method can achieve higher accuracy and efficiency.