To obtain the cable force under dead load, the data was recorded during the closure of bridge by the health monitoring system of an existing bridge. Firstly, the linear relationship was obtained between the cable force and temperature through correlation analysis, and the results were verified by simulation results of finite element model. Secondly, the temperature sensitivity of the different cable force was analyzed using the finite element model. The stay cables deeply affected by the temperature include the short cables on both sides of the tower, longer cables near the assist pier of side span and long cables of the mid-span. Finally, nine years' monitoring data were selected and assessed based on correlation of slope coefficient and variable weight synthesis principle. The results show that the cable force assessment model effectively reflects the uniform change and non-uniform change of cable forces.