An improved linear driving force approximation is proposed for the description of adsorption dynamics of a spherical, porous sorbent pellet subject to a step change in the surface concentration. It was formulated by incorporating the time dependence of mass transfer coefficient into the equation. Compared to the classical linear driving force approximation, which is characterized by a constant mass transfer coefficient and displays large errors at the initial adsorption stage, the present one exhibits rather good accuracy particularly at short times. With slight modifications, the developed approximation can be adapted for the calculations of dynamic responses of cyclic adsorption-desorption operation. The computational results also reveal that the present approximation can provide accurate estimations for cyclic operations with both short and long cycle periods.