Abstract: From the perspective of enterprise niche theory, this paper first defines the niche width degree and niche overlap degree indicators of international contractors and then proposes appropriate measurement methods to describe the diversification and utilization of international market resources, as well as the similarity of the international target market and the level of competitiveness among contractors. According to the business volumes statistics of the world's largest 250/225 international contractors published by ENR each year, enterprises niche of international contractor from total 13 major countries are measured. Then enterprises niche statuses of international contractors from different countries in the complex international market environment are analyzed quantitatively. Finally, comparative analysis between the Chinese and the United States international contractors are given. The results find:the European and American contractors hold higher niche width degrees compared with those of Asian contractors; the contractors in different countries with higher niche width also have higher niche overlap degree; the main competitors of Chinese contractors are firms from U.S.A, Germany, Korea, Japan, U.K., Italy, and Australia. Chinese contractors are at the stage of rapid development, and it is necessary for them to improve comprehensive capacity and to develop new international market.