The work aims to study effects of duty cycle parameters on surface morphology and mechanical properties of TiAlSiN coating by depositing TiAlSiN coating on the surface of cemented carbide substrate by adopting multi-arc ion plating. Morphology of the coating was observed with scanning electron microscope, and mechanical properties of the coating were detected with automatic scratch tester and nano indentation tester. With the increase of duty cycle (10%~70%), the ion bombardment was strengthened, and the coating surface was greatly improved, large particles and tiny-pit defects decreased gradually. However, large particles and tiny-pit defects increased as the duty cycle increased to 90%. Nano-hardness, elastic modulus and adhesion of the coating first increase and then decrease as the duty cycle increases, and reach the maximum value of 48.15 GPa, 518.24 GPa, 50.55 N at 50%, respectively at the duty cycle of 50%.