The increase of pore water pressure under a dynamic load is an important reason for the vibration liquefaction of saturated sand. Therefore, studying the dynamic pore water pressure model of tailings sand plays an important role in the seismic liquefaction analysis of tailings ponds. In this paper, the dynamic pore water pressure development characteristics of tailings fine sand and tailings silt in a tailings pond with the centerline method are studied by dynamic triaxial tests. The research results show that the liquefaction dynamic pore pressure ratio of tailings fine sand shows a trend of "rising–smooth–rising" with increasing vibration frequency ratio, and the liquefaction dynamic pore-pressure ratio of tailings silt shows an approximate linear and stable increasing trend. According to the development law of dynamic pore pressure, a new tailings sand pore pressure stress model is proposed in this paper, and the fitting effect is compared with four different pore pressure models, which verifies the applicability of the new model to predict the growth of dynamic pore pressure in tailings and silt.