Abstract: Mental time travel refers to the faculty that allows humans to mentally project themselves backward in time to relive or forward to pre-live events. Mentally reliving past events is also known as episodic memory in the literature. Mentally reliving future events is also known as episodic future thinking. Previous studies have found that past and future mental time travels share phenomenological characteristics and activate similar brain parts. Other studies have found differences between them, with individuals leaning more towards the future. Of particular relevance to the phenomenon of future bias are studies that have examined temporal emotion asymmetry. Temporal emotion asymmetry refers to people experiencing greater affect when thinking about the future than the affect they experience when thinking about the past. This is true for both positively and negatively valenced events. Emotion differences between past and future thinking are robust and emerge early in development. Previous studies found that temporal emotion asymmetry appears to be present in children from at least 6 years onward, and once established the size of the temporal emotion asymmetry effect did not vary by age or scenario. This article explains the temporal emotion asymmetry from the perspectives of mental simulation and psychological distance. First, the difference between future and past mental simulation may be an important factor affecting the temporal emotions asymmetry. Mental simulation refers to how an individual projects himself onto different events, spaces, or hypothetical reality, a human-specific ability. Compared to simulating past events, people who simulate future events are typically based primarily on focal aspects of events to the neglect of more peripheral event features or aspects of the event context that might moderate affective impact, and this can systematically lead to overestimations of the affective impact of events in the future. Second, one reason people are more emotionally oriented to the future is that the future is psychologically closer to the past. The reduction of psychological distance leads to an increase in the intensity of emotional experience. TEA can influence temporal value asymmetry and temporal asymmetries in moral judgment. (1) Temporal value asymmetry refers to people’s tendency to value future experiences more than equivalent experiences in the equidistant past. For example, Individuals believe they should be paid more for doing the same job a month later than when they did a job a month ago. The reason why they make these asymmetrical valuations is that contemplating future events produces greater affect than does contemplate past events. (2) Logically, an unethical behavior performed yesterday should also be unethical if performed tomorrow. However, previous studies suggest that the timing of a transgression has a systematic effect on people’s beliefs about its moral acceptability. Future transgressions are judged to be more deliberate, less moral, and more worthy of punishment than equivalent transgressions in the past (we will label these temporal asymmetries in moral judgment). Because people’s emotional reactions tend to be more extreme for future events than for past events, such emotional reactions often guide moral intuitions, and judgments of moral behavior may be more extreme in prospect than in retrospect. Future research directions include (1) Temporal emotion asymmetry under different temporal orientations. Temporal orientation, also known as temporal focus, refers to the degree to which people pay attention to the past, present, and future, as well as the tendency to produce emotional and behavioral responses to these time zones; (2) Considering the temporal emotion asymmetry of depressed groups; (3) Exploring the differences in temporal emotion asymmetry from different perspectives.