The work aims to prepare nanocomposite Cr-Al-Si-N coatings with nc-(Cr,Al)N coated by a-Si3N4 by adding Si element to Cr-Al-N coating through advantages of high ionization rate and high sputtering energy in high power impulse magnetron sputtering technology and then control the microstructure and compositions of coatings by varying the N2/Ar ratio during the reactive deposition to improve the coating performance. Cr-Al-Si-N coatings were prepared by high power pulse and pulsed DC composite magnetron sputtering. The influence of N2/Ar ratio on the composition, microstructure and mechanical and tribological properties of the Cr-Al-Si-N coating were investigated systematically in virtue of scanning electronic microscope, X-ray diffractometer, energy spectrometer, stress tester, nano-indenter, scratch tester, and friction tester. The coatings were composed of face-centered cubic CrN and AlN phase and all the coatings exhibited (200) preferred orientation. The adhesion of coating/substrate was the best as the N2/Ar ratio was 3∶1 and the critical load reached about 36.5 N. The friction coefficient and internal stress were as low as 0.5 and -0.48 GPa, respectively. When the N2/Ar ratio was 4∶1, the H/E and H3/E*2 reached a maximum value of 0.11 and 0.24 GPa, respectively, and the wear rate linearly decreased to 1.9×10-4 μm3/(N?μm). When the N2/Ar ratio is 4:1, the Cr-Al-Si-N coating prepared by three-target co-sputtering has higher hardness and better wear resistance.