In order to solve the steady state seepage flow of tunnel vault leakage without sediment influx, an explicit analytical solution of the steady state seepage field of the vault leakage was derived by combining the conformal mapping method and the separate variable method. The PLAXIS finite element software was applied to establish a numerical model to verify the correctness of the solution obtained in terms of the seepage field distribution and the lining water pressure, and the accuracy of the solution was illustrated by comparing the seepage volume with the existing analytical solutions, the numerical solutions and the experimental results. A parametric analysis was carried out to investigate the effect laws of the tunnel burial depth and the seepage width on the lining water pressure and the seepage volume. Results show that the lining water pressure decreases significantly within ±60° of the centre of the leakage location, with the increase in the tunnel burial depth the maximum lining water pressure decreases, the seepage volume first decreases and then increases, and the tunnel burial depth corresponding to the minimum value of the seepage volume increases with the increase in the surface water head. As the leakage width increases the maximum lining water pressure decreases and the seepage volume increases. When the leakage width exceeds 0.05 m, the effect of changes in the width on the water pressure and the seepage volume is less. Leakage control at low leakage widths is effective.