She joined the civil service in August 1985 and rose to her present rank of Administrative Officer Staff Grade A in April 2008. Miss Fong has served in a number of bureaux and departments, including:
- the former Administrative Service and Information Branch
- the former City and New Territories Administration
- the former Government House
- the former Finance Branch
- the former Constitutional Affairs Branch
Miss Fong has also served in a number of senior positions in recent years, including:
- Deputy Director-General, Hong Kong Economic and Trade Affairs, Washington (August 1997 to September 1999)
- Deputy Secretary for Transport (later retitled Deputy Secretary for Environment, Transport and Works (Transport)) (October 1999 to June 2004)
- Director-General, Hong Kong Economic and Trade Affairs, Washington (August 2004 to July 2006)
- Commissioner for Economic & Trande Affairs, US (July 2006 to October 2008)
- Commissioner for Tourism (November 2008 to Dec 2009)