Tsao was first elected to political office in 1992 as a member of the National Assembly. In 1994 he was elected as a councillor in the Taiwan Provincial Council, at which point he left his career in education to become a full-time politician. In 1998 Tsao won a seat in the Legislative Yuan representing the Democratic Progressive Party; he was reelected in 2001. In 2004 the Pingtung County magistrate Su Jia-chyuan was appointed Minister of the Interior, leaving the way clear for Tsao to run for county magistrate in 2005. After winning the election in 2005 Tsao was reelected in 2009. He did not stand for reelection in 2014.[3]
After the DPP's landslide win in the 2016 9-in-1 elections, President Tsai Ing-wen appointed Tsao Agriculture Minister in her first cabinet.[4] Tsao stepped down from the position in February 2017.[5]