Thermal barrier coating (TBC) was applied to Co based superalloy specimens, where bond coat was CoNiCrAlY deposited by high velocity oxygen fuel (HVOF) spraying and top coat was 8 mass% yttria stabilized zirconia (YSZ) by atmospheric plasma spraying. After heat cycles with different holding temperature, holding time at the maximum temperature and heat cycle numbers, edge indent tests of the specimens were carried out to measure the delamination energy of the coating. The results showed that the delamination energy Ed once increased and then decreased with increase in heat cycle numbers. The Ed was lower than those obtained from holding tests at high temperature. The delamination life of TBC was calculated by combining the effects of heat cycles (thermal fatigue) and holding time (oxide growth) on the damage of interface using the strain parallel to the substrate. The predicted delamination life coincided relatively well with experimental one.