In order to eliminate the pollution of lubricating oil vapor in engine compressor air bleed to cabin air supply and its impact on the operation of air dynamic pressure bearings， and improve the cabin air supply quality of a certain type of transport aircraft， a centrifugal compressor driven by a power turbine is proposed to replace the engine compressor as the pressurized air source. On the basis of improving the temperature control path of the air cycle system， a new environmental control system is formed with the centrifugal compressor as the pressurized air source. The performance calculation method of the new environmental control system is given， and its performance is calculated within the flight envelope. The calculation results show that the outlet air parameters of the new environmental control system meet the requirements of the transport aircraft for the environmental control system. In the hot weather， the new system can save at least 10.3% of the engine air bleed flow compared with the original system. In other weather conditions， the engine air bleed flow can be greatly saved， even more than 60%. The research shows that the new environmental control system can adapt to the change of cabin thermal load to reasonably use the engine air bleed flow， and reduce the engine power consumption of the environmental control system.