The innate nature of Marx capital is commodity, which includes related contents of the duality of capital mentioned by scholars. Addible capital is just one of the three forms of capital of Marx. The fault of the academic circle is that they generalize this form of capital as the only one. Limitations of capital of Marx are as follows: regarding the remnants of slavery at early stage of capitalist society as general phenomena of capitalist mode of production; his strong hatred for capital and capitalists hinders his objective and fair recognition on capital.