Thick thermal barrier coatings are used in the protection of hot-end components of aero-engines becauseof their excellent thermal insulation effect. After serving in a high-temperature gas erosion environment, the denseand thick thermal barrier coating flakes off locally and fails. In this paper, the cross-sectional morphology, elementdistribution, phase structure of the coatings after failure has been investigated. The results show that the mainreason for the failure of the coating is the infiltration of surface attachments and the increase in internal stress ofthe dense and thick thermal barrier coating under flame erosion. The service life of thick thermal barrier coatingwith dispersed cracks prepared by high-energy plasma spraying is expected to be improved.