In order to predict the settlement of soft soil foundation for retaining water dam in construction period and operating period,the paper studied the settlement rule of soft soil foundation and the dissipation law of pore water pressure.The result can offer a reference for the design and construction of dam and the settlement forecast of similar soft soil foundation.The paper analyzed the settlement rule of soft soil foundation under retaining water dam in construction period and operating period by use of finite element analysis software. The results showed that the settlement and the horizontal displacement of soft soil foundation increase rapidly in construction period and tends to stable in operating period. The maximum settlement is 2.077m, and the maximum horizontal displacements inside and outside the dam are 1.351m and 0.8376m.The pore water pressure increases first and then decreases with the increase of time and load, and finally is reduced to zero. The maximum pore water pressure is 31 kPa.