In recent years, the United States has successfully launched several new generation GPS Ⅲ satellites. The

observations quality of satellites directly affects the stability, availability and accuracy of the system positioning service, so it’s very

meaningful to evaluate and analyze the quality of GPS Ⅲ satellite observation data. The data quality of GPS Ⅲ and GPS Ⅱ

satellites were analyzed and compared in terms of signal-to-noise ratio (SNR), data integrity rate, multipath effect and observation

noise with the observations of six Multi-GNSS Experiment (MGEX) stations. The result shows: the SNR, pseudo-range multipath,

and pseudo-range observation noise of GPS Ⅱ and GPS Ⅲ satellites are at the same level, the data integrity rate of GPS Ⅲ

satellites in each frequency band is very stable, and the carrier phase observations have a good consistency.