Focusing on the difficulty in monitoring and judging the credibility of user behaviors in online applications and the problem of weak theorey of user behavior credibility analysis, a credibility analysis method of online user behavior was proposed based on non-interference theory. Firstly, the static credibility of single behavior was defined from three aspects-the behavioral entity identity, state and environment of the single behavior, and the static credibility verification strategy was given. Thereafter, dynamic behavioral credibility was defined from the perspectives of execution process and result, and dynamic credibility verification strategy was given. Finally, the user behavior process was constructed based on the single behavior, and the credibility determination theorem of user behavior process was proposed based on the idea of credibility extension, and the theorem was proved by using non-interference theory. The correctness and validity of the proposed method were verified by the provement process and result.