Abstract: This study focuses on the changing mechanisms of gender imbalance in China’s population transition, including the declined population growth, the increased aging and the increased urbanization. With the perspective of population transition data and policy adjustment, this study will analyze how gender imbalance and consequences change in the circumstance of population transition and policy adjustments on family planning, aging supports and urbanization. Based on national census, annual population survey and policy documents, the results indicate that the declined fertility rate will possibly lead to more marriage squeeze among surplus men; due to the distributary of family resource by marriage cost, the situation of aging will make families be confronted with more economic challenges, and the consequences of gender imbalance will spread across generations; urbanization and rural-urban migration make gender imbalance of rural communities spread geographically, and both rural and urban communities will be confronted with gender imbalance. The results of policy analysis indicate that fertility policy adjustments is one of important power that improves the governance on gender imbalance; aging policy adjustments suggest the direction of aging service in policy system and will lead the governance on gender imbalance to social governance; combined with urbanization policies, the governance on gender imbalance will become to the comprehensive policy system for both rural and urban communities.