The route selection of seacrossing tunnel is very important. Hence, the geological factors that affecting the construction safety of subsea tunnel is analyzed, and based on marking system, a fast evaluation model for route selection of Mawan seacrossing tunnel is proposed from the perspective of geological adaptability of tunnel route and factors such as geological conditions, design scheme and construction method. The model includes 6 indices, i.e. plane curvature radius, longitudinal gradient, antifloating coefficient, tunnel buried depth, horizontal distance from the plane control factors and differential settlement. When the indices, except differential settlement, cannot meet the design requirement, one vote system should be adopted. The influences of groundwater level, soil properties, soil thickness, preconsolidation pressure, vehicle load, etc. on differential settlement index should be considered when calculating tunnel settlement by layersummation method. Meanwhile, the radius of settlement curvature is divided into 5 levels after calculated by empirical method. Thus, the fast route evaluation model of Mawan seacrossing tunnel is established and then embedded into the threedimensional parametric selection line analysis platform, which could realize rapid selection of tunnel geological parameters and fast evaluation of route selection. According to the fast route evaluation model, the scores of the 3 shield routes of Mawan seacrossing tunnel are 79.3, 71.3, 84.1, respectively, which can provide reference for the selection of tunnel route.