The study was to explore effort of planning parameters by analyzing the result of Gamma pass rates for IMRT verification for Pinnacle planning system.5 Head Neck IMRT plans finished by Xio planning system were imported into Pinnacle planning system. Different algorithms and calculation grids were used to calculate the dose distributions for 3 orthogonal planes at isocenter which were exported in 3 kind grids. Mapcheck software was used to calculate the Gamma pass rate using the plane dose distributions from Xio system as the reference ones simulating the measurements.The difference of Gamma pass rates for 3 kinds of algorithm and calculation grids were of statistical significance.The parameters in Pinnacle planning system may have influence on Gamma pass rates. It needs further discussion to directly use the Gamma pass rates in documents during the establishing of IMRT QA protocol.