Tainan County Government was established on January 7, 1946, governing “districts” instead of “counties,” and siang or jhen became the terms used to denote townships. Later, the two townships of Shueishang and Taibao were redrawn as parts of Chiayi City, Anshun Township was redrawn as a part of Tainan City, and four townships, Lin’nei, Mailiao, Baojhong and Dongshi were set up anew, with the Alishan Aboriginal Territory changing to Wufong Township. At this point, the jurisdiction of Tainan County included 10 districts with 15 jhens, 52 siangs (townships), 1,166 villages, and 15,649 neighborhoods. On April 9 of the same year, the government relocated from Tainan to the present address in Sinying. On October 25, 1950, after the administrative districts were redrawn, the jurisdiction of Tainan County included only five of the original districts, which were, Sinying, Sinhua, Sinfong, Beimen, and Zengwun, with seven jhens, 24 siangs (townships), 499 villages, and 6,901 neighborhoods.
On February 2, 1968, Syuejia Siang was upgraded to Syuejia Jhen. On December 25, 1981, the seat of Tainan County Government, Sinying Township, was changed to Sinying City. Later, in light of its rapid increase in population, and according to Article 7-2 of the Implementation Outlines of Local Governance for Townships and Cities in Taiwan Province, townships with a population of over 150,000 may be established as a county municipality, Yongkang Township was upgraded to Yongkang City on May 1, 1993. After the latest adjustment (March 1999), Tainan County today includes two cities, seven jhens, 22 siangs (townships), 521 villages, and 9,638 neighborhoods.