Element Free Method only needs to solve node information in domain and calculate domain boundary condition without need of any element information and it is easy to handle, with high computing efficiency. Dynamic radius of influence selection scheme is adopted and nodes are arranged flexibly, which can effectively reduce leveling effect. Penalty Function Element-free Method is used in this paper to study the steady seepage field in main dam that is with protective concrete slab and structure of hydrofracture grouting cutoff wall, of Dashi Bu reservoir located in Donghai County, when it is normal water level for the reservoir, and compare the errors between measured value and computed value from piezometer tube. The analysis shows that computed value is fully in line with measured value; distribution of seepage and free surface conforms to universal law, so Element Free Method can solve seepage issue of fill dam under complex condition.