By using the GAMIT soft，the water vapor content of atmosphere was retrieved based on the ground－based GPS data from January to October 2009 in Tazhong station．The diurnal variation curve of PW were obtained by analyzing averaged data of each month．The results are as follows:the diurnal variation of the whole year’s water vapor content in the hinterland of the Taklimakan Desert was obvious and it presented a sine curve．The maximum appears at 08:00 and 23:00 with the values of 13．63 mm and 13．85 mm．The minimum appears at 01:00 and 14:00，12．91 and 12．28 mm，respectively．Atmospheric water vapor content is the least in January with the average value of 7．09 mm，and the minimum value was 0．95 mm at 13:00 on January 21 in winter of 2009．And it is the most in July with the value of 20．01 mm，the maximum value is 34．75 mm at 07:00 on August 6 in summer of 2009．The maximum diurnal variation range of water vapor content is in October，and there is not significant fluctuations in February．