In order to study the regeneration performance and mechanism of aged asphalt in high altitude regions of plateau, seven kinds of reclaimed asphalt with different regenerant contents were prepared. The properties of reclaimed asphalt were evaluated by the dynamic shear rheological test (DSR) and bending beam rheological test (BBR). The Fourier transform infrared spectrometer (FT-IR) and atomic force microscope (AFM) were used to analyze the recycling mechanism of aged asphalt and reclaimed asphalt with different regenerant contents. The results show that with the increase of regenerant XT-3 mass fraction, the penetration and ductility of reclaimed asphalt fluctuate greatly with the increase of the content, and the penetration and ductility reach the maximum value when the XT-3 mass fraction is 7.0%. When the XT-3 mass fraction is 7.0%, the test value of the softening point is the smallest. The complex modulus first decreases and then increases, and the phase angle first increases and then decreases. The rutting factor and fatigue factor first increase and then decrease, and the creep speed first decrease and then increase. The surface roughness of reclaimed asphalt is greater than that of aged asphalt, and the infrared spectrum results show that there is no chemical reactions between the regenerant and the asphalt. Considering the road performance of reclaimed asphalt, the optimum mass fraction of regenerant is 7.0%.