To research the seawalls stability against sliding under high tide level in construction period, limit equilibrium and finite element shear strength reduction methods were used to analyze the stability with the physical and mechanical parameters from indoor tests. Under the effect of self-weight, rainfall, wave and earthquake, a certain seawall under high tide level is stable for both upstream and downstream slopes from simulation results. However, the rapid changes of tide levels may lead to decreasing the stability of seawalls, and the higher the tide level, the bigger impact on seawalls.The rainfall and earthquake may also decrease the stability of seawalls. The long-effect mechanism of the wave to seawall stability should also be focused in the study.