Abstract: The L-band secondary windfinding radar-radiosonde system is the essential equipment of the atmosphere measuring.The SNR of receiver is the key to improve the measuring precision of this system.To achieve this aim,a new L-band secondary windfinding radar-radiosonde system was built.This system adopted the monopulse and phase-scanning technic to improve the measuring precision.According to the SNR,this article analyses the measuring precision of the new system,and deduces a conclusion that the system's performances satisfy the requests.