In order to safely and rapidly go through sections with unfavorable geological conditions during the construction of subsea tunnels, advanced curtain grouting scheme for uneven weak surrounding rock of subsea section between Xiamen IslandXiang′an Subsea Tunnel on Xiamen Metro Line 3 is studied. The construction efficiency of the original design grouting scheme of "99 holes and 25 m of longitudinal reinforcement range" is low, hence, it is optimized by "56 holes, 25 m of longitudinal reinforcement range and sectioned grouting". The scheme after optimization includes: (1) The radial reinforcement range is 5 m away from the excavation face and contour line. (2) The longitudinal reinforcement range is 25 m. (3) The slurry diffusion radius is 1.5 m. (4) The distance of end grouting hole is 2.2 m. (5) Two kinds slurry materials, ordinary Portland cement and ultrafine cementglass water, are used. (6) The final pressure of grouting is 0.5-1.5 MPa. The application results show that: (1) The efficiency of hole sweeping is improved to more than 200 m/d. (2) The grouting efficiency increases by more than 3 times. (3) The average speed of construction reaches 1.72 m/d, which is 2 times the traditional construction speed. The rationality and effectiveness of the optimization scheme are proved.