Long-term sorption and multi-step desorption of p-Nitrochlorobenzene (p-NCB) on two soils and humic acids were studied by using bath equilibrium methods. The results showed that both sorption amount and nonlinearity of isotherm were time-dependent, which were increased as the sorption time prolonged. Initial aqueous concentration had great effect on the sorption rate of p-NCB. It needed more time to reach sorption equilibrium for the lower concentration samples than for the higher ones. For the two soils tested, both the one- and two-steps desorption isotherms could not overlap with the sorption isotherms, indicating the strong sorption hysteresis of p-NCB on the two soils. As concerned with humic acids, although the sorption of p-NCB on them presented a nonlinear characteristic (n=0.794), the one- to four-steps desorption isotherms were almost overlapped with the sorption isotherms. All the sorption and sequential four-steps desorption data fell on almost a same line, with a correlation coefficient (R2) of 0.988 by logarithmic scale linear regression, which indicated that the sorption of p-NCB on humic acids was almost completely reversible.