Abstract: Theoretical study was carried for a temperature programmed desorption process between hydrogen isotopes and 5A molecular sieve surface based on physical absorption dynamics and experiments of chromatographic separation hydrogen isotopes for many years. Desorption rate formulas were derived under four conditions of first-step non re-absorption and first-step re-absorption and second-step non re-absorption and second-step re-absorption, and dynamic characteristics of desorption process was identified by the calculation of shape parameters and desorption activation energy.