Map merging is a crucial technology for cooperative mapping of multirobot system. A multirobot grid map merging method based on SURF (speeded up robust features) algorithm is studied. In the approach, the robot motion coordinate system is transformed into a rigid body. The mathematical model of the grid map merging problem is establishmented as minimization problem of image registration. Firstly, an improved SURF algorithm is used to extract the features from the grid maps. Secondly, the RANSAC (random sampling consensus) algorithm is employed to eliminate the mismatch and get the initial merging parameters, and the merging parameter is used as the initial value of the ICP (iterative nearest point) algorithm to solve the objective function. Finally, the open datasets and the Turletbot2 mobile robots are adopted for experiments. The experimental results verify that the proposed method can achieve good robustness and high accuracy in the grid map merging by multirobots, the fast speed of map merging indicates that it is suitable for large scale environment.