Laboratory tests and field trials show that compared with the radar sounding system, the Chinadeveloped GPS sounding system, which uses the satellite navigation wind measurement system for wind and the derived pressure from GPS heights for pressure, has higher accuracy and precision. Its electrical performance, stability, and reliability meet the requirements of CIMO. Laboratory tests show that using the new humidity and pressure sensors in the new test conditions, the errors of accuracy are at ± 01 ℃, ± 2%, and ± 1 hPa, within the WMO requirements of conventional upper air sounding. Compared with the RS92 sounding system, the dynamic measurement performance of domestic GPS radiosondes, except for the accuracy of the relative humidity, is close to the RS92 level, especially pressure, geopotential height, wind direction and wind speed that are related with the GPS positioning, whose standard deviations of the consistency are almost equivalent to those of RS92 As for measurement accuracy, the domestic GPS radiosonde is overall better than the operational Lband sounding system.