Lin's father Lin Kwun-rung was a Kuomintang spy. The government sent him to China in 1956, where he was jailed until 1980. Following his release, Lin Kwan-rung spent three years at his ancestral home in Fujian until, with the help of his wife, he returned to Taiwan in 1983.^[1] Lin Cheng-chieh studied political science at Tunghai University, and attended graduate school at National Chengchi University.

Lin was known as one of "three musketeers" of the tangwai movement, alongside Chen Shui-bian and Frank Hsieh.^[2][3] He ran as a tangwai candidate and won a seat on the Taipei City Council in 1981.^[4] Lin won reelection in 1985.^[1] The next year, the defendants involved in the Kaohsiung Incident began serving their prison sentences. Lin was credited with leading a protest calling for democratization, an action that became a catalyst for the establishment of the Democratic Progressive Party, of which Lin was a founding member.^[5][6] His leadership of this protest earned Lin another nickname, the "street bully."^[7] Months after the protest, Lin was stripped of his office upon being imprisoned in September on charges of libel.^[8][9] Lin accused Hu Yi-shou of financial impropriety. Alongside libel charges, Hu filed a second lawsuit against Lin, claiming that Lin had violated election law in his 1985 campaign.^[10] In February 1987, Lin's sentence was extended by eight months.^[11] Within the DPP, he led the Progress faction, a collective opposed to Taiwan independence.^[12] Lin left the DPP in June 1991,^[13] shortly after Fei Hsi-ping and Ju Gau-jeng, leading the party to radicalize and openly support Taiwan independence.^[14][15] After leaving the DPP, Lin told Alan M. Wachman in July 1991 that "[I]t is not necessarily the case that those who identify themselves as Taiwanese support Taiwan independence... I know a lot of socialists who support reunification. But they speak Taiwanese. They are not willing to speak Mandarin."^[16] Lin, who had been elected to the Legislative Yuan in 1989 under the DPP banner,^[17][18] served most of his first term and all of his second term as an independent, stepping down in 1996. In September 1993 Lin founded the New Parliament Magazine, a newsletter-like publication with a Pan-Blue editorial line.^[19] In 1994, Lin began a hunger strike as part of a larger protest in support of retaining a statue of Guanyin on the grounds of Daan Forest Park.^[20] Despite having left the Democratic Progressive Party, Lin served as deputy mayor of Hsinchu under fellow DPP founder James Tsai.^[21] Lin later became the chairman of the Chinese Unity Promotion Party.^[22]

In August 2006, Lin slapped and kicked Chin Heng-wei [zh], editor of the magazine Contemporary Monthly, during a joint appearance on Formosa TV.^[23][24] He was widely criticized by Pan-Blue and Pan-Green political leaders.^[25] The Million Voices Against Corruption, President Chen Must Go campaign, a movement he had supported, forbid Lin from participating in a sit-in protest against Chen Shui-bian.^[26] However, Lin was permitted to attend a protest outside the Presidential Office led by the group in September.^[27] The Taipei District Prosecutors' Office charged Lin with inflicting bodily harm on Chin Heng-wei in October 2006,^[28] and Lin was eventually sentenced to a 50-day prison term.^[29] In August 2007, Lin and others were indicted for their actions during the Presidential Office protest.^[30][31] Despite the indictment, Lin continued small protests against Chen by founding the Nine Nine Association.^[32] In December, he led a gathering of thirty people to protest the renaming of Chiang Kai-shek Memorial Hall.^[33] When Chen stepped down from the presidency in 2008, Lin petitioned Chen's successor, Ma Ying-jeou, to bring corruption charges against Chen.^[34]

In the 2012 legislative election cycle, Lin ran as an independent candidate in Taitung.^[35] During the 2016 presidential election, Lin supported Hung Hsiu-chu's campaign.^[36][37] After Terry Gou lost the 2019 Kuomintang presidential primary, Lin left the party.^[38]

Lin was married to musician T. C. Yang.^[10][39] He later married Lin Feng-ying.^[35] Lin Cheng-chieh died at the Taitung branch of the Mackay Memorial Hospital, on 3 June 2025, at the age of 72.^[40][41] His family disclosed that Lin had adenocarcinoma of the lung for eight years.^[42]