To enhance the high-temperature stability of zirconate pyrochlore structures, one has to focus on their transformation to the disordered state, fluorite. An atomistic simulation calculation is presented in this paper to predict the propensity of rare earth zirconate pyrochlores to transform to fluorite at high temperature. By detailed calculation of defect formation energy of cation antisites and Frenkel pair, as well as their interactions, the mechanisms of disorder transformation are ascertained. The results show that the tendency of cation disorder is less than the anion’s and disorder transformation will accelerate in advanced stage. The calculation of defect energy in pyrozirconates with different cation on the A site have proved helpful in unraveling their different order-disorder transformation tendency.