Abstract: In this study, the author conducts an in-depth research of the electronic commerce protocol CMP1 and finds the problem of redundant design of CMP1 protocol. Besides, the CMP1 protocol does not meet the requirements of fairness and timeliness and it is likely to suffer replay attack and problems like that. In view of the insufficiency of CMP1 protocol, this study puts forward the corresponding improvement scheme and put modifications on the protocol. The improved CMP1 protocol makes up for the previous flaws. Then, the color Petri net protocol analysis method is adopted to model and simulate the modified CMP1 protocol and the properties of the new protocol are analyzed as well. The simulation results prove that the improved protocol can not only meet the requirements of accountability, fairness and timeliness but also avoid the possibility of replay attack.