In order to investigate the feasibility of virtual static load test method to evaluate the stiffness of the main girder of a large span cable-stayed bridge, a cable-stayed bridge was subjected to static load test and modal test under environmental excitation. Based on the modal parameters identified under the environmental excitation, the modal expansion of the measured vibration pattern of the cable-stayed bridge was carried out by applying the kriging interpolation method to predict the modal deflection of the span section of the cable-stayed bridge under the static load test, and compare the measured static deflection with the measured static load. The deflection calibration coefficients under virtual static load were calculated to evaluate the stiffness of the main girder of the cable-stayed bridge. The results show that the modal test under ambient excitation can accurately identify the modal parameters of the bridge; the relative error between the first four orders of vibration patterns predicted by the kriging interpolation method and the measured static load deflection was less than 10%, which meets the requirement of engineering accuracy and indicates the engineering accuracy of the modal deflection applied to large span cable-stayed bridges; the difference between the virtual static load test method and the static load test obtained deflection The difference between the virtual static load test method and the static load test deflection coefficient was small, and the evaluation results were less than 1.0, which indicated that the main girder of the cable-stayed bridge was in good bearing condition, fully demonstrating the feasibility and effectiveness of the virtual static load test method in evaluating the stiffness of the main girder of large-span cable-stayed bridge under normal traffic.