中國大陸即將於2008年實行內、外資企業所得稅率統一政策,使原本33%的內資企業所得稅率與15%的外資企業所得稅率皆統一為25%。早期以優惠的外資企業所得稅率吸引外商投資的中國大陸,如今在面臨外資企業所得稅提升的情況下,對其社會福利的影響為何?本文參考Janeba (1996)、Chen and Wu(2005)分別建立理論模型與實證分析,探討外資企業所得稅率變動對中國大陸社會福利的影響。理論部分發現,當外資廠商的邊際利潤小於內資廠商時,則外資企業所得稅率提高會損害地主國(中國大陸)的社會福利;實證部份也發現外商投資有利於中國大陸的經濟發展,若提升外資企業所得稅率,使外資企業利潤減少,降低外商投資意願,可能會損害中國大陸的社會福利。 In 2008, China will bring unified enterprise tax policy into effect, originally 15% foreign enterprise tax rate and 33% domestic enterprise tax rate will be unified to 25%. In the past, China government offers preferential tax rate in order to attract foreign direct investment, but now, how the rising foreign enterprise rate affect China’s social welfare? We base on Janeba (1996)、Chen and Wu(2005) build up a theoretical and empirical model and analysis the social welfare effects of China enterprise tax reform of switching a dual tax system to a unified system. In the theoretical part, we find that if the foreign marginal cost is less than domestic marginal cost, then abrogating preferential foreign tax rate would damage host country’s social welfare; in the empirical part, we find that foreign direct investment will be beneficial to China’s economic develop. If a rise in foreign enterprise tax rate would reduce foreign profit and hence an incentive for foreign direct investment, then this policy could damage China’s social welfare.