This paper proposes a medium access protocol, CSMA/CD-R (Carrier Sense Multiple Access/Collision Detection with Reservation), designed for a distributed robot system based on wireless network without any centralized mechanism. It employs stations to reserve a communication channel after communication collision such that it shows better performance than conventional CSMA protocol for the wireless communication of the distributed robot system. The effectiveness and applicability of the proposed protocol are demonstrated by carrying out both computer simulations and real experiments with the developed multi-robot system.