A comparative analysis is made of the radiosonde－Lband radar system and the 59701 system by means of the onemonth synchronously observing data from the Jiuquan station, and the change of the data after the introduction of the Lband radar system is evaluated. The results indicate that generally speaking, the temperature, height, wind direction and velocity did not change obviously after using the Lband radar system; the relative humidity difference between the two systems increases with increasing altitude; the accuracy of the humidity records in the upper troposphere is improved obviously.