bstract： In order to calibrate detection efficiency fast and accurately, a realtime numerical method was proposed for measuring radiation of low and medium radioactive waste based on the spatial distribution of detect objects, collimator, and taking the HPGe detector as an example. This method can calculate detection efficiency of point source with different locations and energies, and the relative deviations are less than 5% by comparing with the results of Monte Carlo calculation. The γray detection system was used to measure waste drum samples of wood and polyurethane with 137Cs and 60Co nuclides, and the relative errors between numerical calculation and experimental measurement were within 12%, and most of them were less than 5%. Thus, this numerical calculation method can be used as an accurate and quick calibration of detection efficiency for radioactive waste drum detection.