A method for assembling an operating member and an adapting member by a robot is provided. According to the method, the operating member is moved to the adapting member in an assembly direction until the operating member reaches the adapting member. A moving mode for adjusting the operating member is determined, in which the moving mode includes one or both of a moving-in-plane mode and a posture-adjusting mode. The operating member is moved in the determined moving mode and applied a force continuously in the assembly direction during movement. It is determined whether a preset condition for a completion of the assembling of the operating member and the adapting member is satisfied. And the movement of the operating member in the determined moving mode is stopped or the applied force is stopped when it is determined that the preset condition is satisfied.