From perspectives of scientific paradigm progress and characteristic of statistic inference, this paper focus on why, how and what kinds of field Bayes statics inference should be applied in psychology. Firstly, because frequency probability inference can’t satisfy the need of testing the reliability of theory while scientific paradigm is progressing in the crisis stage and revolution, so some kind of statistics inference which can test the reliability of theory should be introduced. Secondly, because of the meaning of Bayes principle and the characteristic of Bayes statics inference, the Bayes statics inference should be applied when one more reliable theory should be selected from theories. At last, the Bayes statics inference should be applied in the theoretic construct and theoretic discussion, and be used in the development and assessment of mental technical products.