This paper focuses on the use of SBS and SBR as the main modifiers to prepare composite modified asphalt (CMA) binder and CMA mixture for the complex climate of the Qinghai-Tibet Plateau, and compared with the performance of SBS and SBR modified asphalt binder and asphalt mixture. The AC-13 was selected for the gradation of asphalt mixture. The effects of long-term thermal oxygen aging on their mechanical and rheologic properties were studied, and the relationship between the properties of asphalt binder and asphalt mixture before and after aging was analyzed. The results show that SBS and SBR modifiers could effectively improve the high- and low-temperature rheological performance of CMA binder, respectively. Furthermore, the comprehensive effect of modifiers could effectively improve the aging resistance of CMA binder. Affected by the performance of CMA binder, CMA mixture could combine the excellent properties of two different modifiers to improve its high temperature rutting resistance, low temperature crack resistance, water and aging resistance performance. Therefore, it has favorable engineering properties before and after aging. By comparing the relationship between CMA binder and CMA mixture properties during the aging process, it was possible to predict asphalt pavement performance trend and life after aging.