In Capital Asset Pricing Model(CAPM), Beta is the only determinant of asset pricing. In this paper, we decompose a firm’s capital into growth opportunity and assetinplace to explore their impact on Beta, and the relationship with the risk of firm’s capital. Our empirical results show that in Chinese stock market, in general, the Beta of growth opportunities is greater than the Beta of assetsinplace, and there is significant difference among industries. Further, if a firm has larger size, higher booktomarket ratio, and lower market competition for the firm’s industry, the impact of growth opportunity on the firm’s Beta is greater, and the difference between the Beta of growth opportunity and assetinplace is also highly significant. The results show that in Chinese stock market, growth opportunity is not only the key determinant of risk of capital, but also the risk sources.