The success of organizational change often hinges on the perception of fairness within a change unit. This group-level organizational change fairness is crucial for enhancing proactive motivation states and fostering positive change-oriented organizational citizenship behavior (OCB). Rooted in the proactive motivation model, this study establishes a comprehensive multilevel framework to investigate the influence of group-level organizational change fairness on employees' change-oriented OCB. It explores the mediating role of three proactive motivational states and the moderating impact of perceived change impact. Analyzing data collected from 597 employees within 107 teams across 43 Chinese companies, our findings indicate that group-level perceived organizational change fairness significantly predicts employees' change-oriented OCB through organizational change self-efficacy, involvement, and positive emotional experiences. Furthermore, the study reveals that group-level perceived change impact moderates the relationship between group-level fairness perception and both change self-efficacy and positive emotional experiences, with stronger associations observed under conditions of low perceived change impact. These insights notably advance our understanding of the cross-level determinants influencing change-oriented OCB through perceived fairness and proactive motivation. Managers should focus on developing fairness perceptions to stimulate OCB by fostering employees' proactive motivation states, particularly during low-impact organizational changes. Our findings provide valuable implications for organizational change management practices.