CAN-bus communication is a kind of the most important mode used in modular underwater vehicle (MUV) to realize the modularization of data communication between unit modules. In this paper, the CAN-bus-based communication system for a MUV is discussed in detail on both hardware and software, and the corresponding hardware communication interface of CAN-bus is designed by analyzing the features of each unit module of the MUV. The standardized communication protocol of CAN-bus application layer with modular communication software is designed according to the features of MUV communication system.