The laminated rubber bearings of in-service bridges are prone to aging, which leads to the time-varying mechanical properties of the rubber bearings, resulting in changes in the structural response under earthquakes action. To explore the time-varying laws of the mechanical properties of in-service laminated rubber bearings, this paper employed the accelerated thermal aging method to age eight laminated rubber bearings for different times. The variation laws of the horizontal force-displacement hysteresis curves, horizontal shear stiffness, and friction coefficients of laminated rubber bearings under different aging times under compression-shear action are discussed. The finite element model of a three-span prestressed concrete diagonal continuous beam bridge is established, and the influence of the stiffness and friction coefficient of the aging laminated rubber bearings on the seismic response of the upper and lower structures of the bridge under different seismic intensities was analyzed. The results show that aging has a significant impact on the mechanical properties of laminated rubber bearings, causing the horizontal force-displacement hysteresis loops of the bearings to become larger. Moreover, with the increase in aging time, the horizontal shear stiffness and friction coefficient of the bearings increase. The time-varying nature of the mechanical properties of aged laminated rubber bearings can reduce the rotational displacement of the superstructure girder of the skew bridge, but it leads to an increase in the seismic forces of the substructure and increases the risk of damage to the substructure. Therefore, the aging of laminated rubber bearings cannot be ignored, and the aging degree of laminated rubber bearings needs to be quantified when evaluating the seismic performance of in-service bridges.