Water vapor tomography is of crucial theoretical importance to and widely applied in meteorology and climatology,for instance,extreme weather forecasting and now casting,numerical weather prediction and climate change study.Conventional water vapor tomography strategy for calculating equation coefficient needs extensive calculation.To solve this problem,projection plane algorithm is developed for improving the speed of calculation and the accuracy of inversion.The GPS signal data used in this article comes from Hong Kong SatRef.The result,which is compared to the traditional algorithm,indicated that new algorithm reduces the computing time greatly and is not affected by size of tomography area and there is consistency in the results of tomographic inversion and radiosonde.