In cognitive radio networks, the number and state of cognitive users and channels vary strongly with time. In complex environments, more factors need to be considered. To evaluate the current performance of various allocation protocols, a performance evaluation system of spectrum allocation protocols (PES-SAP) based on a probability distribution vector is proposed in this study. The system can flexibly evaluate channel allocation protocols. Moreover, an equitable and random allocation protocol is proposed herein to enable maximum secondary users to obtain channels for the available spectrum. The PES-SAP is used to evaluate the comprehensive performance of the equitable and random allocation and traditional random allocation protocols. The simulation results show that the PES-SAP can clearly distinguish these two protocols and some of the equitable and random allocation protocols have better performance within a certain number of values in the random allocation agreement.