Abstract: A modified Wilzbach method——the melt substrate exposure method is developed, whichgives a tritium labelling efficiency 5.2 times higher than that of the original Wilzbach exposure, and, if during the melt exposure a high frequency electric discharge is passed through the tritium gas for 10 minutes, the tritium labelling efficiency becomes 46 times higher than the original method.It seems that the labelling is more efficient at the melting point of the substrate than at room temperature (25℃).The tritium labelling efficiency obtained is directly proportional to the pressure of the tritium gas when the pressure is less than 40 mmHg, but it is nearly constant when the pressure is raised above 40 mmHg.