The work aims to study the oxidation behavior of the TiAlSiN nanocomposite coatings on the Ti6Al4V alloy at 800 ℃ by a cyclic oxidation test. A series of TiAlSiN coatings with different Si contents were deposited on the titanium alloy and Si(100) substrates through modulated pulsed power magnetron sputtering (MPPMS) by controlling the nitrogen/argon flow ratio fN2. The constituent, phase composition, microstructure and hardness of TiAlSiN were characterized by X-ray diffractometer, scanning electron microscope, electron probe, transmission electron microscope and nanoindenter, and the microstructure and morphology of TiAlSiN coating after cyclic oxidation test at 800 ℃ were analyzed with X-ray diffractometer and scanning electron microscope. When the average pulse power was 2 kW, fN2 increased from 10% to 30% and the Si content (by atomic weight fraction) increased from 6.1% to 16.4%, but the contents of Ti and Al decreased accordingly. When fN2 was 10%, the TiAlSiN coatings with the nitrogen content of about 47% were observed as x-ray amorphous structure. When fN2 increased up to 30%, the TiAlSiN coatings had the distinct TiAlN X-ray diffraction peak together with the amorphous phase. TEM indicated that the nanocrystalline grains in TiAlN coatings were about 5 nm and embedded in the amorphous matrix. All the TiAlSiN coatings deposited on Si substrate exhibited the similar nano-hardness, modulus and residual compressive stress of about 17 GPa, 225 GPa and -300 MPa. The TiAlSiN coatings with the distinguished nitrogen contents and characteristic microstructure were deposited under the fN2 of 10% and 25% and selected as the protective coatings to study the cyclic oxidation resistance. The TiAlSiN coatings had better oxidation resistance at a higher temperature of 800 ℃ for 70 h, compared with the original Ti6Al4V alloy. The coatings with high silicon contents under the fN2 of 25% exhibited the obviously better cyclic oxidation resistance than that deposited under the fN2 of 10%, and oxidation layers on the TiAlSiN coatings were composed of three sublayers, i.e. rich α-Al2O3, and a-TiO2 and r-TiO2 sublayers with the dense columnar structure from top to bottom. The TiAlSiN nanocomposite coatings with high silicon contents have lower oxidation rate, and the nanocomposite structure and low compressive stress are the main factors to improve the cyclic oxidation resistance of the coating.