In this study, we proposed the non-combined cycle pressurized IT-SOFC system for efficient use of compression hydrogen energy in a gas cylinder, and the possibility of the system was discussed by comparison of the SOFC power gain by pressurization and power consumption gain of an air compressor. Oxygen partial pressure pO2 management on cathode side is also important because pO2 directly influences to the polarization resistances. For estimation of the power densities as functions of air utilization Uair and pressurized air remaining factor Χ(=(pO2,cathode-0.021 Uair)/(0.21(pair-0.1))), the ac impedance data of a micro tubular single cell, which was developed in ceramic reactor project, was measured under the several pO2 conditions on cathode side at atmospheric pressure (0.1MPa) and 0.3MPa. Area specific activation polarization resistance Rpol.act and concentration polarization resistance Rpol.conc. were obtained from the the ac impedance data, and the power generation curves of SOFC bundle under the several Uair and Χ conditions were simulated using the Rpol.act and Rpol.conc.. These simulations suggested that if Χ is high enough, i.e. over 0.5, pressurization could dramatically reduce Rpol.act and Rpol.conc. even at Uair=0.95. Based on these simulated power generation curves of the SOFC bundle, the preconditions of SOFC system were expanded up to 10kW class for practical comparison between SOFC power and power loss by the air compressor. This comparison is suggested that the maximum actual power Wact. of pressurized SOFC at 0.3MPa can be higher than that of atmospheric pressure SOFC if Χ is over c.a. 0.5. The Χ and Uair must be kept high enough for the high performance operation. It is found out that effective exhaust of low pO2 gas from system is important for holding the high Χ.