Disclosed is a power saving mode control system (200) and method in a wireless portable Internet system. Stations in the sleep mode are grouped by aligning listening intervals of the stations which enter the sleep mode in the power saving management system wherein the sleep interval for receiving no traffic data is exponentially increased. Therefore, the sleep mode of the grouped subscriber stations are easily managed, and power saving efficiency is enhanced and system complexity is lowered by easily and quickly detecting data states provided to the corresponding stations.