In order to study the influences of concrete shrinkage and creep and environmental temperature change on the evolution of stress state of main girder of self-anchored suspension bridge, under vehicle load during long service period, the ANSYS refined solid finite element model of Hunan Road Bridge in Shandong Province was established. The stress variation laws of extra-wide box girder bottom plate under the conditions of concrete shrinkage and creep in 30-year operation period and temperature rise of 5 ℃-20 ℃ were analyzed. The results show that with the increase of bridge service life, the longitudinal compressive stress of box girder bottom plate decreases gradually, and the longitudinal tensile stress of 0.085 MPa appears in some positions after 30 a. The transverse tensile stress of 2 MPa appears at the junction of box girder bottom plate and the outermost web, and the layout of transverse prestressed reinforcement needs to be optimized. When the bridge has been in operation for 30 a, the longitudinal tensile stresses at the junctions of box girder bottom plate and inner webs reach 1.06-2.70 MPa, under 1.0-1.6 times of symmetrical equivalent design live load. When the bridge has been in operation for 30 a and the ambient temperature rises by 5 ℃, the longitudinal tensile stresses in some areas of box girder bottom plate exceed the tensile strength of concrete under the designed symmetrical equivalent live load. The temperature rise of 20 °C makes the maximum longitudinal tensile stress of bottom plate reach 8.65 MPa.