You Ching was born in 1942 in Xuejia, Tainan. After graduating in law from National Taiwan University he studied in Germany and took a doctorate in law at Heidelberg.

At the 1980 Kaohsiung Incident trials he was one of the fifteen defense lawyers, sharing the remaining defendants with Chang Chun-hsiung and others. That same year he won an added seat on the Control Yuan, one of the few tangwai figures inside the five-branch system. In the weeks before the Democratic Progressive Party was founded at the Grand Hotel in 1986, he, Hsieh Chang-ting, Yu Shyi-kun and others drafted its platform and charter in secret.

In 1989 he was elected magistrate of Taipei County — the first time the DPP won the county. He was re-elected in 1993 and served eight years in all. Taipei County then had close to three million people, more than Taipei City, but none of a special municipality's budget or staff; the county government and the central government argued over money and authority almost the whole time he was in office. Taipei County did not become a special municipality, New Taipei City, until 2010.