Junyu dingzhong 軍餘頂種 was a key step in the development of the military reclamation system during the Ming dynasty, which promoted the formation and development of soldier-farmer families. Previous studies have overlooked the historical background and practical process of junyu dingzhong. Additionally, due to a scarcity of historical materials, research regarding the social implications of junyu dingzhong has not been sufficiently thorough. The newly discovered Tax Book of the Fukou Farming Battalion 明代洑口屯田糧清冊 from Yongtai county contains numerous historical details regarding junyu dingzhong in the Fukou farming battalion of the Yanping guard in Fujian province during the Chenghua period. This study indicates that the loss of military colonies and farming armies was the major dilemmas faced by garrisons in Fujian since the Zhengtong period. The cultivation of land in military colonies became the common task of junyu in garrisons. Junyu cultivated the land of military colonies owned by former soldier-farmers and garrisons, which had been redistributed to military colonies based on the amount of tax subscribed by junyu. This often led to the settlement task being divided among several soldier-farmers families and was a significant transformation of the military reclamation system in the Ming dynasty.The family organization of soldier-farmers gradually took shape in the institutional practice of junyu dingzhong. Soldier-farmer families were a cultural invention that arose from the reform of the military land reclamation system. The core family members were soldiers serving in the army and the junyu who cultivated land in military colonies as farming battalions. Junyu dingzhong provided institutional and financial support for the formation of soldier-farmer families and influenced the construction of family historical memories. In the practical process of junyu dingzhong, military colonies controlled by weisuo were shrinking, while the scope of the military reclamation system was expanding. This complex process of historical change demonstrates the multi-component institutional situation and provides a typical case for re-examining the military reclamation system reformation in the middle of the Ming dynasty.