For dam sites affected by multiple seismogenic tectonics, providing reasonable estimation of ground motion input is the prerequisite to achieve the goal to prevent collapse of high dam under near-field earthquake. The purpose of this study is to establish a method for determining near-field ground motion parameters suitable for engineering applications for sites with complex seismic and geological environment. Firstly, the applicability of stochastic finite fault method in near-field large earthquake simulation is analyzed. The results show that this method can not only describe the fault rupture of the real situation but also can consider the attenuation of seismic wave path and site with high computational efficiency. This method solves the problem of matching the complex source parameters with the computational efficiency in seismic simulation, and thus can be applied estimate the seismic parameters of dam site. Secondly, based on the parameters uncertainty analysis of the stochastic finite fault method, a comprehensive evaluation system of ground motion parameters is established, considering the influence of different seismogenic tectonics on the dam site. The new evaluation system includes the setting range and level of parameters for source, path and site condition, the design of multi-scheme(multi-weight)ground motion simulation scheme, and the calculation principles and methods for determining the weight coefficients of each parameter. Finally, a parameter estimation method characterizing different seismic hazards is obtained. By the method proposed in this paper, the complexity of the seismogenic tectonics near the dam site can be taken into account, the evaluation results with multi-level and multi-risklevel can be given, and reasonable ground motion for the seismic safety evaluation of the dam under near-field earthquake can be provided.