Surface/interface structure is crucial to the service performance and safety reliability of mechanical parts. To study the failure behavior of surface/interface structure under the action of thermal and mechanical, cobalt-based cladding layer was prepared on FV520B substrate by plasma cladding technology, the surface/interface structure of the cladding layer was detected through thermal fatigue test, tensile test at normal/high temperature, and the microstructure was observed by a scanning electron microscope and a metallographic microscope. Results show that cobalt-based cladding layer has excellent thermal fatigue resistance at 600 degrees C, and the fatigue resistance of the surface/interface structure of cladding layer decreases with the increasing of temperature, and the fatigue crack originates in the interface between the coating and the substrate. The coating breaks in the uniaxial tensile experiment, and further studies show that the coarse dendrite are broken at the multilayer lap position. In high-temperature tensile experiment between 300 and 700 degrees C, the surface/interface structure of cobalt-based cladding layer failes inner the coating at various temperatures, while the failure position transferres from the coating to the substrate as the strength of the cladding layer increased with the addition of alloy elements.