In this study, Sasobit, as an asphalt modifier, was blended into two base asphalts- Pen 60/80 asphalt and SBS modified asphalt. The additional content of Sasobit was 2%, 3%, 4% and 5% by mass of asphalt. The Rolling Thin Film Oven test (RTFO) and the Pressure Aging Vessel test (PAV) simulate the asphalt's short-term aging and long-term aging separately. Two sets of evaluating systems (Penetration-grade system and Performance-grade system) were conducted on the asphalt's properties in three different aging states (the original state, the short-term aging state, and the long-term aging state). The high temperature properties of asphalt improved, and the lower temperature properties of asphalt declined. The variation trends in the three different states were also expressed by using the linear regression. The durability of the asphalt was evaluated based on these aged trends. It was evident that the durability of asphalt binder was related not only to the additive content but also to the asphalt binder type and aging state.