For a long time, the search for a relationship between mood and mental health has been taking place in two seemingly contradictory but closely related directions. The powerful destructiveness of negative emotions and the protective and promoting role of positive emotions are often the focus of research in this field. However, theoretical and empirical studies in recent years have shown that it is insufficient to draw a comprehensive conclusion on the relationship between emotions and mental health by focusing solely on the role of positive or negative emotions. How the simultaneous experience of positive and negative emotions, namely mixed emotions, can affect mental health is a question worth discussing, which provides a new idea for the research on the relationship between emotions and health. The Co-activation Model of Healthy Coping suggests that mixed emotions enable individuals to find meaning from stressful events, gain a sense of control over their lives, and turn adversity into strength. When experiencing both positive and negative emotions at the same time reaches the optimal balance, the most beneficial health outcomes can be achieved. The Dynamic Model of Affect also points out that the ability to experience mixed emotions under pressure is beneficial to the health of individuals. Such a state of uncoupling between positive and negative emotions enables people to freely obtain positive experience and healthy emotional state even under pressure. He Model of Positivity Ratios emphasized the effect of mixed emotions on mental health from the perspective of positive psychology, and put forward a concept similar to Co-activation Model on the relationship between the two. Mixed emotions promote mental health mainly in stress coping, happiness and psychotherapy. In stress coping, mixed emotions are conducive to reducing negative experiences brought by stressful events, promoting the integration and processing of complex information, and problem-solving oriented behaviors, as well as improving coping efficiency. The effect of mixed emotions on happiness lies in that it can help individuals comprehensively consider the positive and negative characteristics of goal conflict in the process of goal realization, balance multiple aspects of complex events, potentially promote the process of meaning creation, and finally obtain happiness experience. Mixed emotions are also seen as a protective factor against the formation of psychiatric symptoms and can predict the improvement of psychological symptoms during treatment. Although the positive effects of mixed emotions on mental health have been supported by theoretical and empirical studies, many scholars have found that the relationship between them is complex and non-linear. The individual's tolerance and ability to deal with the conflict and ambivalence of mixed emotions may be the key variable affecting the relationship between mixed emotions and mental health. Individual and cultural characteristics related to tolerance and handling ability of mixed emotions, including construal level, mixed emotion experience pattern and cultural differences, have moderating effects on different degree in the process of mixed emotion promoting mental health. Mixed emotional experience is a common psychological state in daily life, which is closely related to mental health. However, previous studies have not paid enough attention to this field, so some important issues have not been fully discussed, which should be paid attention to in future studies: (1) An accurate description of the non-linear relationship between mixed emotions and mental health. (2) To determine whether mixed emotions have different effects and mechanisms on mental health in low-stress situations (such as adaptation and interpersonal communication) and non-stress situations (such as entertainment and consumption). (3) The internal and external mechanisms of mixed emotions promoting mental health should be discussed in detail.