To ensure the safety of excavating connection aisle in a cross-river-tunnel, the excavation process is numerically simulated by finite difference software FLAC^3D to directly perceive the mechanical features of freezing soil curtain under high water pressure and to investigate the effect of coupled seepage stress on the stability of the curtain. The effect of water level variation on the mechanical features of freezing soil curtain are obtained through numerically analyzing the distribution of displacement field, stress field, and seepage field. It’s found that forces on the curtain are more evenly distributed owing to pore water pressure. The bottom and middle of the curtain, which is more likely subject to stress concentration, should receive more attention. The study provides reference for the simulation of connection aisles and the artificial freezing construction.