Forgiveness is defined by prosocial changes for people’s transgression-related interpersonal motivations toward a transgressor. When people forgive a transgressor, they become less motivated by revenge and avoidance and more motivated by benevolence toward the transgressor. Previous studies have found that forgiveness process needs time to achieve motivation change, however, the intra-individual changes of forgiveness is not conformity with the linear or curve until now. McCullough et al. (2003) showed that a linear trend fit on the development of forgiveness, whereas Pronk et al. (2010) indicated that the forgiveness curve showed a curvilinear trend. Therefore, the growth model of forgiveness needs further studies to resolve this paradox. Meanwhile, the available evidences have shown that forgiveness are negatively associated with rumination, however, the evidence does not yield clear conclusions regarding the effects of rumination that as a personal characteristics on forgiveness process. Hence, the second objective was to study the effects of rumination on the intercepts and slopes change of interpersonal forgiveness. The Transgression-Related Interpersonal Motivations Inventory (TRIM) was used to assess the forgiveness. There were eighteen items to measure Revenge subscale, Avoidance subscale, and Benevolence subscale. Rumination was assessed with the Chinese version of Ruminative Response Scale (RRS). Participants were 116 undergraduates (M=21.61, SD=1.35), and 41.6% were male. We recruited undergraduates who had experienced a serious transgression within the past 7 days through undergraduate psychology courses. Qualified participants received preliminary questionnaires including TRIM and RRS. After returning these questionnaires, they were scheduled to complete up to five follow-up TRIM in the online every 1 weeks. We used HLM to test our hypotheses. We first examined how interpersonal forgiveness unfolded over time. The results showed that a linear model best fit our data on the development of revenge motivation and avoidance motivation. That indicates the avoidance and revenge motivations toward their transgressors are linearly drop down. However, a curvilinear model best fit the dimension of benevolence motivation. That means the level of benevolence motivation increases faster in the first few weeks after the offence, but do not increase substantially after a certain point. Second, we investigated the impact of rumination on the process of interpersonal forgiveness. Model analyses demonstrated that rumination had significant impact on the intercepts and slopes change of avoidance, revenge and benevolence motivations. Results of the current research contribute to the studies examining the temporal nature of forgiveness. We provided some evidence for the linear trend for the negative dimension of forgiveness, but the nonlinear trend for the positive dimension of forgiveness. These results support the importance point of view to distinguish the dimensions of forgiveness. On the other hand, this study constituted the effort to explore the effects of rumination on forgiveness. Analysis results supported the rumination is the influence factor of forgiveness process. This study allows us to better understand the forgiveness mechanism through improving the levels of rumination.