The construction of fine 3D geological modeling is one of challenges in realizing true 3D visualization of geological body.Based on Triangulate Irregular Network（TTN） and Corner Point Grid（CPG） spatial data model

we propose a hybrid spatial data model for constructing fine 3D geological model.Firstly

a tectonic-stratigraphic framework model is set up based on TTN.Then

the framework model is converted into fine volumetric 3D geological model based on CPG voxel data model

and thus the fine expression of inner space of 3D geological body is achieved.During the converting process

it is necessary to define the order of strata.The mesh of the geological body is further realized by calculating the spatial coordinate of each grid cell and validating and saving data file in GRDECL format.Finally

the fine geological model is displayed by inputting the file into QuantyView3 D system.A fine 3D hydrogeological model of the key area of a coastal city is constructed successfully by using the proposed method

and the feasibility of this method is verified.