In this paper, we adapt the partial order state reduction techniques developed for Petri nets and labeled transition systems to the validation ofmulti-process protocols modeled as communicating finite state machines. We identify two specific partial order reduction methods in this context: (1) maximal partial order reachability analysis, which is a generalization of maximal reachability analysis to protocols with n\ge 2 processes; and (2) simultaneous partial order reachability analysis, which is a counterpart of fair reachability analysis for protocols with n\ge 2 processes and arbitrary communication topologies. We study the logical error detection capabilities of each method and show that these two methods, when used together, provide complete logical error coverage for bounded multi-process protocols.