Abstract: In the last two decades, the capital profit rate had taken on a declined trend, while the total output was increasing in industry section. In this article, we proposed three assumptions to explain this phenomenon. The statistics studies which base on the data of 1963 -2003 suggests that: the factors that affected the capital profit rate have large changed between the two different periods. The descent of capital efficiency in the period of economic reformed can be attributed to: the deviation of technology option, the increased of firms‘ quantity and the accented of input-material price.