Concrete faced Rockfill dam (CFRD) is a safe and economical dam type in hydraulic engineering. The temporary dam body for flood control during construction period is usually used for CFRD, so the safety of temporary dam body during construction period is very important. Based on numerical simulation of the seepage field of the temporary dam body of CFRD using nonlinear FEM (Finite Element Method) under the action of flood of the river during construction period, the stability of the dam slope is studied. The effectiveness and applicability of the method introduced is certified through computation in the study on the practical project. The paper provides an effective analysis method for the study on the stability of dam slope of the temporary dam body of CFRD for flood control during construction period.