In the future fifth generation (5G)systems,non-orthogonal multiple access (NOMA) is a promising technology that can greatly enhance the network capacity compared to orthogonal multiple access (OMA).In this paper,we propose a novel random access (RA) and resource allocation scheme for the coexistence of NOMA-based and OMAbased machine-to-machine (M2M) communications,which aims at improving the number of successful data packet transmissions and guaranteeing the quality of service (QoS)(e.g.,the minimum data rate requirement) for M2M communications.The algorithm of joint user equipment (UE) paring and power allocation is proposed for the coexisting RA (i.e.,the coexistence ofNOMA-based RA and OMA-based RA).The resource allocation for the coexisting RA is investigated,thus improving the number of successful data packet transmissions by more efficiently using the radio resources.Simulation results demonstrate that the proposed RA and resource allocation scheme outperforms the conventional RA in terms of the number of successful data packet transmissions,thus is a promising technology in future M2M communications.