Abstract: This paper proposes a direct method to determine thecomputational degree of freedom W of bar systems in a way of simplicityand uniformity. By taking the bar between any two adjacent joints and thejoints as the analysis objects, the direct method gives a formulaW =3 m -(3g+2h) for the plane system with m bars, g single rigid joints and h single hinge joints. Compared with the previous algorithms to determine W, this method is easy to be applied and may increase the accuracy and the efficiency. It can also be used in determining the degrees of freedom of a statically indeterminate problem.