Some research showed that power can promote prosocial behavior; while other research suggested that power can suppress prosocial behavior. However, this study proposes that whether power promotes or suppresses prosocial tendency depends on the current situation. According to Situated Focus Theory of Power, powerful individuals have higher selective attention and more flexibility to process information, so they can identify relevant situational information and ignore the information irrelevant to the current situation, whereas powerless individuals tend to process different types of information more equally. Individuals primed with power can always show behavior consistent with the situational goals. Powerful individuals will show more prosocial behavior when the present goal is to gain more self-benefits and show less prosocial behavior when the context leads to gain less or loss of self-benefit, which indicates perceived self-benefit is a potential mediator. To sum up, this study aims to solve the debate that when power promotes prosocial tendency and when suppresses prosocial tendency. This study includes 2 studies to explore the underlying psychological mechanism of the power influence on prosocial tendency in cooperative context and competitive context and also to test the mediation effect of perceived self-benefit. All the participants were recruited in their employment when participating our experiments. We recruited 271 participants in Study 1 and 139 participants in Study 2. In Study 1, we only manipulated context (cooperative VS. competitive context) to explore how sense of power influence prosocial behavior. We also used a scale to measure their general sense of power. Participants were randomly assigned to a cooperative or competitive context. Then they completed measures of prosocial behavior tendency and other demographic measurements. In Study 2, we both manipulated power and context. Participants were asked to recall a power-related event to manipulate their high/low sense of power and subsequently were asked to describe the event and how they felt during this event. Then participants were assigned to read the context material (cooperative context or competitive context) randomly. Finally, participants completed measures of prosocial tendency, self-benefit perception and other demographic measurements. Study 1 shows that different situation can moderate the relationship between general sense of power and the tendency of prosocial behavior. Study 2 further reveals that individuals primed with high sense of power always exhibit behavior consistent with the situation, (1) perceived self-benefit turns out to be a significant mediator between the sense of power and prosocial behavior, (2) cooperative and competitive context turn out to be the moderating role between the sense of power and perceived self-benefit, (3) and people primed with high sense of power who can perceive to gain more self-benefit in the cooperative situation will tend to exhibit more prosocial tendency, while tend to exhibit less prosocial tendency because they perceive less self-benefit in the competitive situation. This study provides supporting evidence for the Situated Focus Theory of Power and expands that perceived self-benefit is an important factor to be considered when it comes to power and prosocial behavior. In addition, the results reveal the underlying psychological mechanism of the power influence on prosocial tendency, perceived benefit as a mediator and perception of current situation as a moderator.