NPV have been widely applied. A majority of the existing calculating methods of cash flow are the static method or the expectation method. It is more reasonable to regard future cash flow as random variable which has certain probability distribution, which shifts with time. But the research about it has been introduced rarely. Through introducing some kinds of existing methods and considering the feature of Markov method, a dynamic method which is used in solved the distributing of indeterminate feature cash flow is showed. So a new kind of dynamic calculation method about NPV is obtained. The method is applied in the calculation to future cash flow of the certain highway investment project of China. The result shows that this method is feasible, effective.