In this paper, a new framework is proposed for the analysis of electronic commerce protocols. Comparing to the framework proposed by Kailar, it has three major improvements. Firstly, it can analyze fairness of protocols efficiently. In the analysis of fairness, it takes the reliability of communication channels into consideration. Secondly, the initial possesion set depends on environment in stead of human beings. At last, by introducing the cipher text understanding rule the new framework can analyze the message which includes signed cipher text.