To face the competition in the business environment, the company should continuously execute the capital investment to reinforce its competitive ability and to insure the endless business operation. Due to the capital investment involving huge money and long-term impact, the company should considerately and thoughtfully evaluate the financial feasibility of capital investment prior to making decision. Weighted Average Cost of Capital (WACC) is usually used as benchmark to evaluate the capital investment. WACC is made up of two key elements. The cost of equity, one of both, however, is difficult to measure. This article, taking C company as an example, is focused on how to apply 3 different models such as Dividend Growth Model (DGM), Capital Asset Pricing Model (CAPM) and Free Cash Flow Model (FCF) to compute the cost of equity as well as on analyzing the outcomes of those models. The outcomes of DGM, CAPM and FCF are respectively 11.82%, 14.2%, and 10.50%, and the highest one is the outcome computed from CAPM. The outcomes computed from both DGM and FCF are narrowly different. As compared with actual rate of return of C company stock (11.6% adjusted from ex-cash dividend and ex-stock dividend), it is found that the outcome of DGM is the nearest to actual rate of return of C company stock, then FCF¡¦s is next one and CAPM¡¦s is most different. However, on condition that the company did not distribute cash dividend in its record or stayed on the abnormal growth stage, the DGM could not be applicable. Internal capital budgeting includes expansion of production expansion, replacement, improvement and innovation. Due to the fact that the attribute of this kind of capital investment is similar to that of the company¡¦s business of line, FCF would be the most appropriate model to estimate the cost of equity to determine the WACC for the purpose of internal capital budgeting evaluation.