MODIS near infrared water vapor products were tested by using the field observations which indicated that the precision of products should be improved and the products were not fit for application over the region. Considering the reasons inducing the error, we improved the algorithm and retrieved water vapor content by adjusting the spatial resolution and using the information of land use type. Our results show that the average relative error is 4.47% ,and the average absolute error is only 0.0456 g/cm^2 , which indicates that the retrievals are much better than the products. By using MODTRAN to analyse, we find good negative correlative relationship between water vapor content and transmittance. According to the relationship, the transmittance was obtained which would be helpful to calculate the surface temperature and other energy parameters.