Today, the manufacturing quality and replication ability of high tech products or materials in China is continuously improving. And Japan, the largest economy entity in Asia, is still the main market for both China & Taiwan to export the high tech products. Therefore, it is a great concern for Taiwan's market share in Japan if Taiwanese high tech companies continue to invest in manufacturing in China. This present paper adopted pooling model to analyze Taiwanese high tech firms' investment in China vs. their market share in Japan over the years of 2000~2006. And the result showed: the investment of Taiwanese high tech industries in China has no significant impact on their market share in Japan due to the competition from China.