Thermal fatigue and isothermal oxidation tests of a plasma sprayed thermal barrier coatings have been carried out. The experimental results indicated that micro-cracking as the fatigue damage occurred in each cooling stage of thermal cycles. And the spallation fracture morphology was changed by the cycle wave form; the spallation failure occurred in the ceramic top-coating under the triangle cycle wave condition, on the other hand, it occurred near the top-coating/TGO interface under the trapezoidal wave condition. The finite element analysis indicated that the local residual stress, which is the driving force of interfacial damage, increases with the thickness of the thermal grown oxide. The degradation mechanism by thermal fatigue was discussed, in addition, a simple life prediction model for the thermal fatigue of TBC systems was proposed.