Abstract: In order to calculate the displacement of the bridge under the nonlinear temperature distribution, the method on support displacement estimation of continuous beam and effective temperature calculation of cross section are proposed based on unit-load method. Then five simplified calculation methods on effective temperatures are established. In order to investigate the accuracies of those simplified methods, the temperature and displacement of the box girder section were measured based on the seven-span variable cross section girder of Fenghe Bridge with a single box 3 rooms located in Xi'an. Experimental and numerical results show that the effective temperature of the cross section is related to the temperature distribution and the shape of the section. For the non-uniform cross section box girder, the effective temperature of different cross section is different even in the same temperature distribution. If the weighted average value of the effective temperature of cross section is calculated by the exponential decay temperature variation across concrete slab for the heat conduction effect, the estimated support displacement would and be relatively conservative with small errors. The numerical results of the finite element method show that the simplified algorithm is reasonable.