Chen Ding-nan was born in 1943 in Sanxing, Yilan, graduated in law from National Taiwan University, and went into private business. In 1981 he was elected magistrate of Yilan as a tangwai candidate, and re-elected in 1985.

As magistrate he was known for refusing gifts, skipping banquets and reading every document line by line; people called him "Clear-Sky Chen." In 1986 Formosa Plastics proposed building its sixth naphtha cracker at the Lize industrial zone in Yilan. He opposed it, for concrete reasons: in winter the north-east monsoon pressed the air down onto the Lanyang plain where it could not disperse, and the county's water sources, paddy fields and river mouth all lay downwind. He asked Formosa Plastics for figures on emissions and dispersion.

In June 1987 he and Wang Yung-ching debated the plan on television; neither convinced the other. Martial law ended that July. In 1988 Formosa Plastics gave up on Yilan, and the plant was eventually built at Mailiao in Yunlin.

After leaving office he was elected to the Legislative Yuan, and in 1994 he was the DPP's candidate in the first election for provincial governor, losing to James Soong. In 2000 he became Minister of Justice and served five years. He died of lung cancer in 2006, aged sixty-three.