he Oxygen absorption processes in highly aligned YBaCuO samples in air and in pure oxygen were studied at several constant temperatures. The process can be expressed in two steps: a chemical reaction controlled step and a diffusion controlled step. The kineticequations are as follows, respectively:The activation energy was calculated by using an Arrhenius equation. The technicalconditions of heat treatment for oxygen absorption of highly aligned YBaCuO crystals are discussed.