On 4th May, the teachers and students of Southwest Associated University held a closing ceremony and inaugurated the Southwest Associated University Monument. The period of the Southwest Associated University had come to an end.
After the war, in 1946, Nankai returned to Tianjin and was reformed into a national university by the government. Zhang Boling held the post of president. Nankai was divided into four schools and sixteen departments apart from the Economic Institute, the Institute of Applied Chemistry, and the Research Center of Frontier Humanities. More famous professors came to lecture, including Wu Daren, Wang Yuzhe, and Bian Zhilin, to name a few. After thirty years as president, Zhang Boling retired in 1948, and He Lian took the post of Acting President.
In January 1949, Tianjin was liberated, and Nankai University started its new journey. It has long been given much attention by the central government. Chairman Mao wrote the name for Nankai University in 1950 and came to inspect the campus in 1958, while Premier Zhou Enlai came to Nankai successively in 1951, 1957 and 1959. Top Chinese leaders like Jiang Zemin, Li Peng, Zhu Rongji, Wen Jiabao and Jia Qinglin all came to Nankai for inspections.
In 1952, after the reshuffling of university organization, Nankai became a comprehensive university of arts and sciences, with fourteen departments and three professional specialties in total. After the reshuffling, Zhang Tianting, Lei Haizong, Wu Tingqiu, Li Helin, Zhu Weizhi, Li Jiye, Ji Taoda, Gu Changdong, Wen Gongyi, Chen Renlie, Jiang Ancai, Zeng Dinghe and Yang Zongqing were transferred to Nankai University; a number of overseas scholars returned and started teaching, including Wang Ganyu, He Binglin, Chen Rongti, Chen Ruyu, Chen Tianchi, Wang Jitao, and Yan Zhida. In 1958, some departments of Nankai, including trade, business management, accountancy, finance, and statistics were transferred to the Tianjin Finance and Economics Institute. In 1960, the Department of Geology and Geography (which subsequently closed in 1961), the Department of Physics II (transferred to Lanzhou University in 1961) and the Department of Philosophy were established. Until the 1980s, Nankai University preserved its nine-department configuration, with schools of mathematics, physics, biology, chemistry, Chinese, foreign languages, philosophy, politics and economics, and history.