In order to better understand the aging of asphalt binders in the asphalt mixture that occurs during their service, asphalt mixture specimens with three different gradations of AC 13, SMA 13, SUP 13 were aged in an accelerated weathering machine(AWM) for various durations. Gel permeation chromatography(GPC) and Fourier transform infrared spectroscopy(FTIR) tests were performed separately on the recovered asphalts. Nonlinear models were established by fitting the measured properties. The results show that the aging rate and aging degree of asphalt binders can be well indicated by the parameters of the established nonlinear aging models. When the aging time is increased, the percentage of large molecule size and middle molecule size from GPC and the functional group of carbonyl from FTIR increase, the percentage of small molecule size and the functional group of butadiene from FTIR reduces; SMA 13 is overall performed the best in the aging resistance among the three tested mixtures.