The influence of gas nitriding on the wear and corrosion resistance of 40Cr steel was investigated. Gas nitriding experiments were carried out at 550°C for 2h and 10h. The microstructure and hardness gradient were observed and analyzed through metallurgical microscope and micro hardness tester. The polarization curves were scanned by the M398 Corrosion Integrated Test System. Using MG-200 high speed friction and wear testing machine did end mill test and calculated the wear rate. By scanning electron microscopy (SEM) observationing the worn surface morphologies. The results show that after different nitriding time, the specimen surface forms with nitrided layer of different thickness, and changes with the hardness decreased with the penetration depth. Furthermore, the gas nitriding treatment may change the corrosion potential positively and reduce the density of the electric current of 40Cr steel. In addition, wear mechanism of the matrix is mainly adhesive wear, but after nitriding is mainly abrasive wear. The wear rate reduces significantly.