Abstract: Land acquisition and resettlement management of mega water conservancy and hydropower projects is a systematic work related to the promotion of projects construction, regional social stability and economic development, emerging complexity characteristics. However, existing studies have not yet systematically explored the management complexity of land acquisition and migration for mega water conservancy and hydropower projects, and there is a lack of attention to complexity coping strategies. Combined with the management experience of mega water conservancy and hydropower projects in Hainan province, this study identifies eight influencing factors for the object complexity, organizational complexity and process complexity for management of mega water conservancy and hydropower projects based on the grounded theory. Then, through the construction of a Fuzzy Cognitive Map (FCM) model for evolutionary analysis, it is found that these influencing factors have a significant impact on the complexity of land acquisition and resettlement management. Among them, the effects of diversified interest demands (X₅), dynamic balance of multiple objectives (X₈), and the diversity of participants (X₄) are the most significant. Combined with the results of FCM predictive analysis, diagnostic analysis, and sensitivity analysis , this study proposes coping strategies by establishing effective communication mechanisms, multidimensional demand collection mechanisms, differentiated negotiation mechanisms, and graded early warning mechanisms. The results help to deepen the understanding of the complexity management of land acquisition and migration in mega water conservancy and hydropower projects, and provide suggestions for the practices of land acquisition and resettlement management.