Abstarct: CrAlN coatings have NaCl cubic structre. According to significant mechanical and tribological properties and high thermal stability, this kind of coatings is used mainly as resistant laxyer in mextal shaping molds, casting molds plastic and abrasive components. In this project CrAlN coating was applied to the 420 steel substrate with cathode arc evaporation. The purpose of this work was improve the speed of deposition rate along with reducing the surface roughness from 0.6 µm to 0.4 µm. At first stage with consider the constant of the machine parameters such as: arc voltage, frequency and bias voltage, variable duty cycle at 4 values of 20%, 40%, 60%, 80% applied separately when it coated and after obtaining the optimum amount of duty cycle, in second step the effect of bias voltage variable in 3 values -50v, -100v, -150v were investigated separately. The mechanical and tribological characteristics of the coatings. Micro structure and thickness of the cooatings with use of scanning electron microscope (SEM), identification of formed phases and determination of crystalline structure by X-ray diffraction (XRD) were investigated.The mechanical properties of coatings, including the hardness and modulus of young were determined by the nano indentation. Corrosion resistance was investigated by using corrosion test (Electrochemestry impedance and TOEFL). At first stage the laxyers thickness decrease with increase of duty cycle, and the increase of bias voltage at second stage.Mechanical properties and young's modul in both stage with increase the parameters mentioned in first step increase from 18.89 to 37.79 and in second stage decrease from 24.60 to 23.96 respectively. The density of corrosion coatings in first stage increase from 2.27 to 3.40 µA/cm2 and in second stage decrease from 2.29 to 1.15 µA/cm2.