Abstract: In order to uncover the inherent relationship of operating parameters in cryogenic distillation separation of hydrogen isotopes, the influences of W_r (heat power of reboiler) on deuterium extraction efficiency, column pressure drop and liquid level were studied under total reflux mode. As Wr increases from 5 W to 12.4 W, the deuterium extraction efficiency increases almost linearly from 88% to 99.6%. Under total reflux mode, the pressure drop along column increases while liquid level decreases with Wr, no flooding phenomenon occurs. With the increase of Wr, operating pressure of distillation column increases from 100 kPa to 190 kPa, temperature of condenser decreases in order to supply enough cold power.