Abstract：Structural analysis of rock masses by 3D visualization technique is the inevitable trend of engineering geologic research. Due to the complexity and irregularity of rock mass structure in large-scale projects，most traditional methods have some limitations on data quantity and analytic speed. Based on NURBS technique and some associated advanced theories，a new approach of 3D visual construction of rock mass structure is put forward. Then，with the measured discrete information and a series of deciphered 2D sections，the 3D visual model of rock mass is realized with guide of viewpoint of system and classification，and corresponding visual analysis，such as arbitrary cutting and digital drilling，on engineering rock mass structure can be performed based on the 3D visual model. It can give a more direct view of the interior structure of rock mass. Finally，the 3D model and visual analysis are applied to simulate rock mass structure in Nuozhadu hydropower station，and the results provide important references to the design.
