Quemoy (Kinmen) is an island close to Quanzhou (Zaitun) and Xiamen (Amoy) port. A large of number of its residents immigrated to Southeast Asia as well as Nagasaki and Kobe in Japan in search of a living after the 1860s. After they eventually accumulated wealth, these transnational overseas Chinese brought their capital back to Quemoy to participate in family, clan or public affairs. In addition, the gender proportion of the population of Quemoy became unbalanced, so women played a major role in local society. After 1949, Quemoy became a battlefront between the KMT and the CCP, as well as the frontline in the confrontation between Cold War blocs. Under military administration, the power of traditional lineages was suppressed and their connections with their fellow countrymen living abroad were severed. For forty-three long years, until 1992, Quemoy was transformed from an open hometown of overseas Chinese into a closed battlefield and forbidden zone.This paper tries to discuss the relationship between social-cultural change and population flow in the modern history of Quemoy. First, I will analyze the historical situation in the society there, including emigration of its young men, the rise of an overseas merchant-gentry class, economics of remittance and its cultural landscape, women's life histories etc. Secondly, I deal with the social reality of Quemoy as a battlefield, including immigration of soldiers, the impact of military governance, the influence of soldiers' consumption, and the social crisis due to the gender imbalance and the military authority's response. Finally, I will generalize from two different social-cultural changes for population flow and gender politics in modern Quemoy.