By using the orthogonality of the orbital angular momentum (OAM) beam and the characteristics of its annular intensity distribution, a method for separating the OAM beam from the Gaussian beam is proposed. This method uses a dual-area mirror in an OAM multiplexed data link. Experiments show that the topological charge of the multiplexed OAM beams can be reconfigured with the aid of a dual-area mirror. Compared with previous separation methods, this method is low cost, easy to implement, easy to integrate, and can freely control the direction of the separated beam. Furthermore, it can considerably reduce the optical power loss and is expected to reduce the bit error rate in the optical communication link.