Through indoor simulation of the thermal degradation process of styrene butadiene styrene block copolymer(SBS) modified asphalt binders under low air concentration(or relative condition without oxygen), the performance of SBS modified asphalt binders under different conditions was tested and analyzed. The results show that in the process of thermal degradation, the crack resistance of SBS modified asphalt binders at low temperature decreased with time or temperature increases; compared with the effects of thermal degradation under low air concentration on microstructure of SBS modified asphalt binders, SBS modified asphalt binders have higher carbonyl and lower butadiene contents during thermal degradation under high air concentration. It is necessary to fully consider the influences of time, temperature and air concentration on SBS modified asphalt binders performance in the production, storage and transportation of SBS modified asphalt binders.