The embodiment of the present invention discloses a cluster communication method and system, a user equipment and a network side device, related to wireless communication technologies. The cluster communication method disclosed in the embodiment of the present invention includes: when a cluster user equipment (UE) is interested in receiving or is currently receiving a a cluster service in a multimedia broadcast multicast service (MBMS) bearer, if the cluster UE judges that it is needed to transmit the cluster service via a unicast bearer, sending a request to a cluster application server (AS) for transmitting the cluster service via a unicast bearer; after the AS accepts the request of the cluster UE and establishes a unicast bearer with the cluster UE, the cluster UE receiving cluster data via the unicast bearer and stopping receiving the cluster data in the MBMS bearer. The embodiment of the present invention further discloses a user equipment, a network side device and a cluster communication system. The technical solution of the present application can be used to achieve a unicast transmission of cluster communication when the cluster user equipment (UE) does not meet conditions for receiving the cluster service via an MBMS bearer, thus ensuring the continuity of the cluster communication service and reducing the impact on the radio access network.