on the analysis of the ageing kinetics model, ageing kinetics equation has been established on the basis of complex modulus. Rheological properties test have been carried out on SBS modified asphalt and base asphalt. The results demonstrate that when asphalt material in ageing process, the hypothesis that complex modulus is inversely proportional to the concentration of reactant assumptions of ageing reaction is established, on the basis of which, ageing kinetics constant has been obtained. Ageing kinetics equation has been validated by using measured data, it shows that, SBS modified asphalt owns higher reaction activation energy, a good anti-ageing property as well, that the measured data can keep accordance with calculated data, which demonstrates ageing kinetics equation is established reasonably on the basis of complex modulus. The equation can well describe rheological state changes of asphalt in ageing process.