Abstract: A new cyclic constitutive model for granular soil material has been presented within the general framework of bounding surface plasticity. In this model the volumetric strain due to stress-dilatancy for a granular material is composed of reversible and irreversible dilatancy components. The former is characterized by its reversibility and dependency on the magnitude and direction of the current shear stress, and conversely, the latter by its irreversibility and dependency on past shear history. New mechanisms and formulation have been presented for description of the reversible and irreversible dilatancy. Influence of the irreversible and reversible dilatancy component on the stress-strain response was also investigated. The effectiveness of the model was verified with comparison between the calculated and observed results.