Columnar-structured thermal barrier coating systems (TBCs) possess a strain tolerant columnar microstructure wherein the gaps between the columns are filled with high-porosity oxides. At high temperatures, columnar-structured TBCs may be eroded via contact with a significant amount of calcium-magnesium-alumina-silicate (CMAS). A numerical model is proposed to estimate the temperature and stress fields of the microcracks induced by the CMAS infiltration. The energy release rate is evaluated to understand the influence of CMAS on the microcracks in the columnar microstructure. The effects of CMAS on the microcrack propagation are discussed in detail by using the extended finite element method. The results demonstrate that both the stress and energy release rate near the microcrack were found to dramatically increase when the CMAS reached the microcrack. Moreover, increasing the time of CMAS infiltration could destroy the thermal insulation provided by the top coat and considerably increase the energy release rate. The present analysis reveals that the vertical cracks are easily to initiate from the microstructure column and coalesce with adjacent horizontal and vertical pores, thereby resulting in premature failure of TBCs via delamination.