He used to travel frequently between Taiwan and the United States (US) for bilateral trade agreement negotiation until the US switched diplomatic relations from ROC to PRC on 1 January 1979.
He also authorized banks to process import-export permits, promoted professional training and introduced a rotating system for economic and trade representatives stationed outside Taiwan.
He was criticised by the Pan-Blue Coalition for not taking a greater role in the Lien-Soong campaign and acting as convener for a private group of economic advisers for President Chen Shui-bian.
Within six months, he managed to settle a five-year dispute with environmentalists that had been blocking Chinese Petroleum Corporation's construction of a fifth naphtha cracker plant.
Moreover, he succeeded in persuading Formosa Plastics Corp to invest in a major construction project, the sixth naphtha cracker plant in Yunlin County.
In November 1991, Siew represented ROC, under the name Chinese Taipei, for the Asia-Pacific Economic Cooperation (APEC) held in Seoul, South Korea.
In 1988-1989, he was appointed as the Vice Chairman of Council for Economic Planning and Development (CEPD) in which during his office term, he promoted major infrastructure projects, such as the straightening of Keelung River, the placement of Taipei City rail lines underground, the construction of the East-West Highway, the diversion of Chichi River and the expansion of Kaohsiung International Airport.
In August 1993, he completed a review of the Six-Year National Development Plan of the ROC and assigned priorities to projects on the basis of availability of resources and the maintenance of financial stability.
In July 1994, he undertook major administrative reform with the introduction of a program to streamline bidding procedures for public construction projects and government procurement.
The action plans proposed in the papers won the approval of APEC support and helped promote Taiwan in the international trade and investment arenas.
Siew was appointed as the Premier by President Lee Teng-hui after the 15th National Congress of Kuomintang held in August 1997 in Taipei.
[7] On 18 March 2000, Siew joined the 2000 presidential election as a candidate for vice president with his running mate Lien Chan.
[10] On 12 April 2008, Vincent Siew met with Hu Jintao at the Boao Asia Forum as part of the Cross-Strait Common Market Foundation delegation, which also included other former and future government officials and business leaders from Taiwan.
Siew's trip aimed to cement further the diplomatic ties between the two countries, and to celebrate King Mswati III's fortieth birthday.
Siew, in his capacity as the honorary chairman of the Cross-Straits Common Market Foundation, attended the Boao Forum for Asia held in April 2014 in Hainan where he met with Premier Li Keqiang.
He added that the two sides should try to maintain the long-term and healthy development of relation by improving the confidence, mutual trust, respect and interaction.
Part of Siew delegation included Mainland Affairs Council Minister Wang Yu-chi and several Taiwanese business people.
[15] Siew is married to Susan Chu (Chinese: 朱俶賢; pinyin: Zhū Chùxián; Wade–Giles: Chu1 Ch'u4-hsien2) with three daughters: Ru-ting (蕭如婷), Ru-fen (蕭如芬) and Jhih-you (蕭至佑).