Abstract: In the finite element numerical simulation of seismic liquefaction and flow on the saturated sand ground, the mesh deforms strongly when the dynamic load increment is large, because of the complexity of the sand constitutive relationship and the soil-structure contact. Such calculation gives poor results without a desired accuracy, and even breaks off. Therefore, to improve the mesh and to optimize the final results, error estimation is required as a basis in the finite element calculation. According to the principle and procedure of the SPR (Superconvergent Patch Recovery) error estimation, the results and error distributions of two recovered fields in typical numerical examples on liquefaction and flow are compared; the reasons to the value differences of the errors are discussed, considering the liquefaction levels and the displacement vectors distribution. This error estimation can provide a referenced calculating accuracy, and a reasonable basis to improve the finite element calculation.