Abstract: Segmented gamma scanner (SGS) is an important technique of quantitative analysis for nuclear scrap and radioactive waste. The wedge-disturbing effect is a source of error. In this paper, the deviation comprehended the wedge-disturbing effect and statistic error was studied. The result was also verified by measurement and Monte-Carlo simulation. The deviation of total mass of radioactive material is insensitive to reasonable wedge-disturbing effect, and more accuracy requirement for each segment needs strict limit for wedge-disturbing effect and statistic error.