Pre-diffusion treatment (high temperature vacuum treatment) plays an important role in the growth of the thermally grown oxide (TGO) on the low pressure plasma spray (LPPS) bond coat surface. Results show that the initial thin oxide scale, formed during deposition process, on the as-sprayed bond coating surface has broken and shrunk to discontinuous oxide particles through the elements diffusion during the pre-diffusion. Two kinds of pre-diffused bond coats deposited in different oxygen partial pressure atmosphere show different results of the average distance between the individual oxide particles on the pre-diffused bond coating surface. In this study, a three dimensional model with thermal grooving theory was developed to explore the essential condition for the scale breaking and explain the differences of these results. This research can provide reference for the preparation optimization and pre-treatment optimization of bond coat towards high performance TBCs.