Y2O3/YOx composite coatings with different YOx adhesion layers were fabricated on 316L stainless steel substrates through reactive magnetron sputtering. The YOx adhesion layers were deposited by radio frequency reactive magnetron sputtering with different oxygen partial pressures at a total pressure of 1.2 Pa. The Y2O3 coatings were deposited by bipolar pulse reactive magnetron sputtering. The relationships between the microstructures, phase compositions, interfacial adhesion of the composite coatings and the oxygen partial pressure used for deposition of the YOx adhesion layers were investigated. The microstructures and phase compositions of the coatings were characterized by scanning electronic microscopy and X-ray diffraction. The bonding strength of the coatings was measured by scratch tester. The results showed that the bonding strength of the Y2O3/YOx composite coatings reached the maximum value when the oxygen partial pressure was 0.18 Pa.