In this paper, we have studied the uptake of orthoxylene/isoamyl alcohol on silica gel as an example to demonstrate a novel methodology for studying multicomponent gas adsorption on solid adsorbent. In the method, the solid adsorbent was filled into a differential adsorption bed, and the bed was inline monitored with near-infrared diffuse reflectance spectroscopy continuously when the adsorption process was taking place. The spectral data recorded during the process were treated with algorithm of locally weighted regression, which constructed a series of partial least-squares models to more accurately predict concentrations of each adsorbate on the adsorbent. These efforts made the method feasible to obtain more thermodynamic and kinetic information about the adsorption process in a more convenient, rapid, economical, as well as straightforward way. With the method, we obtained the isothermal lines of the multicomponent system at 293.15 K, and the instantaneous adsorption rate of each component during the whole adsorption process.