Abstract: Aiming at the environment modeling for mobile robot, a hybrid environment model including characteristics of both topological map and geometrical map is proposed, named grey qualitative model. The free space of environment is decomposed into a group of convex polygons by convex decomposition algorithm. The convex polygons and the adjacency relationship between them compose the qualitative level of grey qualitative map, which is used to simulate high-level qualitative reasoning for path planning of human. The quantitative level is composed of coordinates and potential field vectors of vertices of each convex polygon, which is used to determine the motion direction and speed of robot in continuous space. Theoretical analysis and experiments show that the grey qualitative map can simulate the expression of environment of human, and can support the robot complete path planning and ensure the smoothness of the path only by adjacency information and vertices infromantion of convex polygons. The proposed method effectively reduces the space complexity of environment model.