In 1917 Tien-Tsai Sung entered military service. From 1925 till 1926 he attended the Military Acadamy in Shensi, China.
Tien-Tsai Sung served successively as battalion, regiment and brigade commander under Gen. Liu Chen-hua. Later he was a commander of the 65th Division and a commander ot the 32nd Army Corps of the 20th Route Army. Then he took the position of Commander of the 75th Division of the National Army.