The steel industry is the foundation that country marches toward modern of development of civilization. According to the International Iron and Steel Institute (IISI) has announced that world crude steel output reached 1,239.5 million metric tons for the year 2006. In 1996, Mainland China produced 101.2 million metric ton of crude steel. By 2001 this had risen to 150.9 million metric ton, an increase of 49.1%. In 2006, China produced 418.8 million metric ton of crude steel, an increase of 313.8% in just ten years. China¡¦s share of world crude steel production has also increased exponentially. In 1996, China became the largest steel producing country in the world. China remains the largest single market and the strongest growth area. Steel use will increase by 13% in 2007 followed by another 10% in 2008 taking the total to 443 million ton by 35% of the world total. Subject that several important environments of steel marketing change, While China poses a severe threat to Taiwan in the Steel market, Taiwanese Steel manufacturers have to move to higher ground ahead of the rising tide of mainland competition. Grounded Theory (GT) is a research method most often associated with the social sciences, (Glaser & Strauss, 1967). Thereafter Strauss in 1990 published Basics of Qualitative Research: Grounded Theory Procedures and Techniques together with Juliet Corbin. Grounded theory was developed as a systematic methodology, and its name underscores the generation of theory from data. When the principles of grounded theory are followed, a researcher using this approach will formulate a theory, either substantive (setting specific) or formal, about the phenomena they are studying that can be evaluated. To research and investigate the changing of supply-chain by interviewing decisive persons in the business, its purpose is to make this thesis more deliberate in study structure and procedures and operational logic. This research can be classified into four main groups, such as raw material suppliers,horizontal competitor,down-stream user and co-opetition(co-operation and competition). The iron and steel industry is combined with four groups, this thesis focus on iron and steel producers. Taiwanese steel industry was forced to face several critical issues from market changing in Mainland China. 1. The industrial down-streamers in Taiwan move to Mainland China. 2.The developments of upper-streamers in China that brings an extra option for purchasing raw material. 3.An increasing stress comes from excess of new established steel companies in Mainland China. 4.The lower- cost substitutes in China invade worldwide steel market. But under the special political situation and common in language and culture, both Taiwan and China industries could have more strategically options in cooperation or competition. It is influencing the key element that this research is probing into China's Mainland and interacting with steel industry of Taiwan, utilize and take Grounded Theoretical research, sum up 129 open coding altogether , sum up 14 axial coding and five selective coding progressively . In order to understand the key elements of the steel industries of both sides of Taiwan Strait.