[2] After having graduated from San Francisco State University, Fan joined the Democratic Party after returning to Hong Kong.

[3][4] Fan opposed the Democratic party's stance on the Five Constituencies Referendum movement and its support of the constitutional reform package in 2010.

In the 2012 LegCo elections, Fan won a new seat in the New Territoires East geographical constituency created under the 2010 constitutional reform package.

[9] He lost his seat in New Territories East in the 2016 Legislative Council election, as Andrew Cheng returned unexpectedly and split the democratic faction's votes.

On 6 January 2021, Fan was among 53 members of the pro-democratic camp who were arrested under the national security law, specifically its provision regarding alleged subversion.

[15] On 2 November, High Court judge Esther Toh upheld her decision to deny bail to Fan arguing that he was a "determined and resolute man" who called for all parties to act together in opposing the government.