He was appointed a Deputy Judge of the District Court of Hong Kong in 1982 and a Deputy High Court Judge in 1991. In 1997, Li was appointed the Chief Justice of the Court of Final Appeal by Tung Chee-Hwa, the first Chief Executive of the Hong Kong Special Administrative Region after the handover. As Chief Justice, he presided in the Court of Final Appeal and was Head of the Judiciary charged with its administration. He served for 13 years until his retirement in 2010.