The invention discloses a quasi three-dimensional map-based mobile robot global path planning method. The method comprises the following steps: 1, reforming a common grid map to a quasi three-dimensional map based on the contouring principle; 2, initially planning: connecting the starting point and the finishing point of a mobile robot into a straight line serving as a current path; 3, scanning the grid passed by the current path, changing to step 6 if a barrier cannot be scanned, or changing to step 4 or step 5 according to the type of a barrier if the barrier is found by scanning; 4, processing the barrier contacted with the boundary, updating the current path, and returning to the step 3; 5, processing barriers which are not contacted with the boundary, updating the current path, and returning to the step 3; and 6, outputting the current path to complete the global path planning. The method sufficiently explores the information of the barriers, improves the execution efficiency of a program, is easy for implementation, and meets the real-time requirement of the mobile robot global path planning.