Abstract: Currently, research on the seepage field of subsea tunnels is predominantly based on single-hole tunnels. Considering that practical engineering often involves the parallel arrangement of three holes and the seepage field may interfere when the tunnels are close to each other, the use of a single-hole tunnel model can result in a calculation error of water inflow exceeding 40%. This article conducts a theoretical analysis of the seepage field in a three-parallel-hole subsea tunnel. Firstly, it assesses the appropriateness of employing the equal area method to simplify the multi-center circular section into a circular section in the theoretical analysis process. Subsequently, the article proposes a seepage field analysis model for a three-parallel-hole subsea tunnel. By utilizing the superposition principle and the image method, the analytical solution for the seepage field of a three-parallel-hole subsea tunnel is derived, and the formula is degraded and numerically verified. The research results indicate that simplifying the multi-center circular section into a circular section using the equal area method has minimal impact on the total water inflow of the tunnel. The proposed analytical solution demonstrates a certain degree of accuracy and can rapidly predict the water inflow of a three-parallel-hole subsea tunnel. Due to the pressure relief effect between tunnels, the distribution of water inflow around the main tunnel of a three-hole parallel subsea tunnel exhibits asymmetry.