Machine to Machine（M2M）communications are widely used in the existing cellular network architecture.However

due to the huge number of M2Mc ommunication terminals

conflicts

network congestion

delay and other issues may occur when a large number of M2M terminals simultaneously initiate random access requests.In order to solve these problems

this paper proposes a group-based random access mechanism which groups the terminals and sets the priority.And the high priority group terminals can be allocated random access resources preferentially.The simulation results demonstrate that the proposed method can effectively reduce the collision probability

save energy

improve the probability of successful access of the terminal and reduce the time delay.