Because it is difficult to accurately determine the effective length and bending rigidity of a hanger, the tension calculation of short hangers according to formula method may lead to big error. Taking the testing of hanger tension of the Xingou River Bridge as the research background, the effects of such parameters as boundary conditions, bending stiffness, effective length and linear density on the accuracy of the tension measurements are analyzed in detail. The results show that the simplifying assumptions of formula method are not suitable for short hangers. Hanger tension calculation with finite element method is introduced. The finite element model is established according to real condition. Firstly, the bending stiffness of hangers is identified; then corresponding relationship table of hanger tension-frequency should be established. The corresponding tension of a measured frequency can be obtained through looking up the table. The method has been applied to construction monitoring of Xingou River Bridge and proved to be an effective method.