Optimization technology is an important method in the decision-making analysis. Analytical Hierarchy Process (AHP) is a decision-making method. It divides the elements of decision-making into objectives, guidelines, programs and other levels. On the basis of these, some qualitative and quantitative analyses are being carried on. The evaluation index system method based on the group's level of AHP not only reflects the advantages of the AHP, but also makes up for the disadvantages. An AHP based on the group's level was put forward to determine the rock covering thickness of the sub-sea tunnels. According to the AHP, a specialist panel should be invited to evaluate the factors which affect the thickness of the sub-sea tunnels. Weight of each the specialists’ judgment is decided according to the ability of the specialists to suggest the most optimized matrix. The minimum thickness of rock covering would be determined finally by the weighted analysis. The new method is named as the AHP of the rock covering thickness of the sub-sea tunnels. This method was applied to analyze the rock covering thickness of Xia ’men sub-sea tunnel.