A multi-module fiber laser capable of monitoring abnormalities of optical modules in real time. In the multi-module fiber laser, the CAN bus is employed to directly obtain whether each of the slave control modules or the master control module is in normal working condition, so that the CAN bus is at the status level corresponding to whether all modules are in normal working state, namely, the CAN bus that is configured to transmit the light control signal issued by the master control module. The status level of the slave control module or the combiner module is also transmitted via the CAN bus, so that all the slave control modules can quickly put themselves in the corresponding working state according to the status level of the CAN bus.