Abstract: The relations and differences between some restrained torsion theories are analyzed in this paper. The discussed theories which are suitable for rigid torsion include Wumansji theory and Reissner theory , the distortion calculation theory which is suitable to distortion load and the seneralized sense coordinate method suitable to both situations. The accuracy of these theories are compared taking cantilever box beam as an example according to the calculation result of finite fold plate shell element method. The results indicate that the accuracy of Wumansji theory is the lowest and the seneralized sense coordinate method gives the best result but needs more time in calculation. The modified Wumansji theory presented by the author can obviously improve the accuracy with simpler calculation.