The present study aim at investigating the possible mechanism by which personality (extraversion and neuroticism) effect emotions. This study introduced one mediating variable (the regulatory emotional self-efficacy, the RESE) to inspect the relationship between personality and emotions from a new angle of view. Basing previous findings, this study made a theoretical assumption that personality influences emotions by the RESE to some extent. That is to say, the RESE plays a mediating role between personality and emotion. 1076 university students were selected to fill 3 scales. The 3 scales used in this study were as follows: (a) the extraversion and neuroticism subscale of the Revised Eysenck Personality Questionnaire Short Scale for China, their Cronbach α among this study sample respectively being 0.79 and 0.76; (b) the revised Chinese version of the Regulation Emotion Self-Efficacy Scale. The scale include four factors: perceived self-efficacy in feeling positive affect (POS), perceived self-efficacy in regulating positive affect (MPOS), perceived self-efficacy in regulating despondency/distress (DES), perceived self-efficacy in regulating anger/irritation(ANG), having good psychometric indicators by the relevant reports. Cronbach α of this scale was 0.78 in this study. (c) Positive Affect and Negative Affect Schedule. Cronbach α of positive and negative affect factors in this study were 0.86 and 0.84. Correlation analysis among extraversion, neuroticism, the RESE, positive affect and negative affect revealed that there are positively correlation between extraversion and positive affect, the RESE and positive affect, neuroticism and negative affect, extraversion and the RESE; negatively correlation between the RESE and negative affect, the RESE and neuroticism. The multivariate stepwise regression analysis suggested that extraversion and the RESE are significant factors in predicting positive affect. Basing on correlation and multivariate stepwise regression analysis, we established a relational model of extraversion, the RESE and positive affect and found that the relationship between extraversion and positive emotion is partially mediated by the RESE. In other words, in addition to direct action to positive emotion, extraversion also influences positive emotion by the RESE to some extent. The mediating effect of the RESE is significantly between extraversion and positive emotion. These findings suggest that the RESE is a key variable during the course of the extraversion effecting positive emotion. Especially, because the RESE is a dynamic structure that can be acquired by way of practice, educators can take measures to promote university students’ RESE and guide them to rely on themselves to managing emotions gradually. The main innovation of this study is taking a new angle of view to inspect mechanism of extraversion effecting positive emotion by establishing a mediating model of extraversion, the RESE and positive emotions. Basing on data result, it came up with that the RESE plays a mediating effect between extraversion and positive emotion.