Abstract: A new algorithm for segmented gamma scanning (SGS) technique was described, by which the activity of radionuclide and the mass of nuclear material in those unknown samples can be determined without calibration by standard sample. Meanwhile, it bypassed the detector calibration and the massive online calculation which are needed in the Monte Carlo simulation, omitted the standards calibration, improved the efficiency of the measurement system, and reduced the requirements for the measurement of waste drums as well. According to the new algorithm described in this paper, the wedge correction has also been considered, which, to some extent, can solve those problems caused by wedge interruption in near-field measurement. Analyzing and comparing the new algorithm results with the results of Monte Carlo simulation, it’s found that these two methods match well, especially with the small segment. Meanwhile, the relative deviation between the measured data of test samples and nominal values is below 10%, which effectively verifies the feasibility of this algorithm.