Abstract: Based on the continuity equation and Darcy's law and the Bernoulli expression, the paper deduces the analytical formula of the water pressure at the key point of the uplift pressure of a check dam laid on horizontal soil in reasonable hypothesis condition. Comparing the results with numerical simulation(Autobank finite element program), the error between the analytical calculation result and the numerical analysis result in this paper is very small, basically less than 1%, which shows the analytical method reliable and stable. The application value of this method is further discussed. Based on the obtained water head, the hydraulic gradient at the downstream x location of the structure can be calculated, the type of seepage deformation of the soil laid on downstream of the structure can be judged, and the range to be treated and the design of the length of the protective tank can be estimated. Referring to the conclusions of relevant literatures, it is proposed that it is safer to use this analytical formula to calculate the uplift pressure of the foundation base of a check dam built on a sloping channel bed. Further study is needed about whether the influence of "effective depth of foundation" to the water pressure of the foundation base needs to be considered in the calculation of uplift pressure of a check dam.