This paper presents a wireless sensor system for monitoring human respiratory activities. The sensor is composed of a fully-integrated CMOS impulse radar chip and a DSP platform that is used for human respiratory feature extraction. The proposed and implemented radar chip was fabricated using in the TSMC 65nm CMOS technology. It can achieve the 1.5mm scanning resolution over the 15m scanning range with total 21mW power consumption. Moreover, the timing circuitry supporting range gated sensing and the pulse generator are all digital standard cell-based design which is very favorable to the technology scaling. The real-time DSP platform captures the wireless data via the CMOS radar chip and processes that through a human respiratory feature extraction algorithm. The entire system can fully operate to validate the performance of the wireless sensor system. Furthermore, the clinical trial was carried on and the system was proved helpful in rapid screen for respiratory diseases.