Abstract: Using beta plastic scintillation counter of low level background, gross beta radlioactivity of twelve samples for high-level liquid waste is determined directly. Beta efficiency curves of plastic scintillation counter for four mass thickness are calibrated in advance. Determining gross beta radioactivity, gross efficiency of the scintillation counter for various energy beta ray is calculated via weighted mean method with the ratio of radioactivity for each nuclide. The ratio of radioactivity for nuclides which havc gamma disintegration is determined in terms of the radioactivity measured by gamma spectrometer. The ratio of the radioactivity for ~(90)Sr which has purity beta disintegration is calculated in terms of halflife lime approximation. The ratio of the radioactivity for ~(147)Pm which also has purity disintegration is calculated by means of apparent cooling-time approximation. The uncertainty of results for the present work is about ±15％.