This paper, according to modern theories of investment decision, designed physical investment decision system. The design of this system, mainly on the basis of both the evaluation of investment proposal and the procurement of fund, consists of the designs of input/output system, the evaluation system of investment proposal, the calculating system of capital cost, and the investment system integrated all the above systems. This system premised the use of computer intended to transform the unreasonable methods of present investment decision making into more reasonable one.