The Airend of water lubricated Oil-free screw compressor adopts PEEK door rotor, aerospace grade stainless steel rotor and a new production process. Using nano-scale water filter core and Inlet reverse osmosis system, it can provide a stable and qualified lubricating water treatment system for the compressor. The oil-free machine system can change water without stopping according to the set water change cycle, reducing daily maintenance costs and making use more worry-free. The system is simple, reduces parts and failure points, and improves reliability. Low energy consumption, isothermal compression, higher volumetric efficiency, more than 15% energy saving than two-stage compression dry oil-free screw compressor.