Kim Sung-tae was born on 9 July 1958 in Jinju, South Gyeongsang Province.

He worked as a labor activist in the Federation of Korean Trade Unions as a young man.

After the 2016 South Korean political scandal, he defected from the Saenuri Party in December 2016 and joined the Bareun Party,[1] but was reinstated in May 2017, before the presidential election.

[2] In November 2017, he was elected floor leader of the Liberty Korea Party.

Later, In June 2018, when Hong Jun-pyo resigned his party leadership, he assumed the acting leader.