The rheological indexes of complex modulus G, phase angle delta, stiffness modulus S and creep slope m were measured by dynamic shear rheological test(DSR) and bending rheological test(BBR). The effects of coupled aging of heat, ultraviolet light and load on the performance of styrene butadiene styrene block copolymer(SBS) modified asphalt were investigated. Infrared spectroscopy(FTIR) was used to analyze the changes of functional groups of SBS modified asphalt after coupled aging. The results show that the aging degree of SBS modified asphalt is relatively serious due to the photothermal coupling effect, while the other two kinds of coupled aging make the aging degree of asphalt smaller. In addition, the effects of three coupling modes on SBS modified asphalt functional groups are different. The photothermal aging of asphalt mainly manifests in the breakage of butadiene bond and the increase of carbonyl group; the thermal charge coupling aging mainly increases the carbonyl group in asphalt; the photothermal coupled aging mainly causes the breakage of butadiene bond and the increase of carbonyl group in asphalt.