Polar precipitable water vapor（PWV） is expected to increase under a warming climate. However, the conventional approach cannot provide sufficient long-term PWV records due to the high maintenance costs. Fortunately, the exponential explosion in the number of geodetic-quality Global Navigation Satellite System（GNSS） stations has broken this deadlock. Utilizing radiosonde and GNSS data over two decades（1994-2020）, we analyzed and evaluated the spatial and temporal variability characteristics of PWV in Antarctica and Greenland. The multi-year mean PWV values for Antarctica and Greenland were 5.63 ± 1.67 mms and 7.63 ± 1.35 mms, respectively, with annual standard deviations（STD） of PWV of 1.60 ± 0.77 mms and 3.44 ± 0.92 mms, respectively. In both Antarctica and Greenland, the PWV annual STD shows a gradual increase from the land center to the edge; while the PWV mean decreases with increasing latitude in Greenland, there is no significant latitudinal correlation in Antarctica. There is no significant regional difference in PWV trends, and from the statistical results, both Antarctica and Greenland show an increasing trend from year to year. The PWV trends in Antarctica and Greenland were 0.29 ± 0.77 mm/decade and 0.27 ± 0.64 mm/decade, respectively, with relative PWV trends of 5.98 ± 12.93%/decade and 3.87 ± 8.45%/decade, respectively.