Thermal Barrier Coatings are used as thermal protective of parts using under high temperature circumstance. These coatings usually include three layers respectively: ceramic top coat, grown oxide layer and bond coat. Due to manufacturing process and special structure of thermal barrier coatings, failure mechanisms of these coatings are affected by applied loads on coated part. In this paper failure of these coating under thermal fatigue was studied numerically and experimentally. A specimen of Inconel 617 which were coated by air plasma method and it was tested in a test setup with capability of applying four point bending load, under thermal fatigue experiment with the maximum temperature of 1170 oC in addition to constant bending load with the magnitude of 7500 Nmm. Thermal fatigue test was contined until coating spallation and temperature of specimen surfaces was measured during the test. Finite elements modeling was performed by ABAQUS to simulate the experiments thermal and mechanical loading conditions with using cohesive zone model to model top coat delamination and failure. Finally with a little change in the model, was attempted to adapt the bending magnitude of the specimen from model on experiment result to estimate interfacial cohesive properties for these coatings from finite elements results.