Respiratory monitoring is important for improving health management and safety. Traditional respiratory monitoring methods often face challenges such as noise interference and deployment costs. In contrast, our passive sensing approach utilizes the channel impulse response (CIR) from existing UWB communication modules, which demonstrates significant application potential due to its high sensitivity to small displacements. In this paper, we propose a human condition monitoring method based on UWB CIR phase information, which realizes the effective extraction and analysis of human respiratory activity by performing a series of signal processing processes on CIR data. A core advantage of this method is its ability to utilize existing UWB communication links, eliminating the need for new radar equipment, which provides a new approach for respiratory monitoring. Experimental results confirm that the system not only accurately monitors the respiratory waveform and frequency at different distances, but also has the ability to detect weak respiratory signals, which is suitable for high-sensitivity scenarios such as child presence detection (CPD). In addition, the method utilizes maximum phase variance channel indexing, combined with the high temporal resolution of the UWB system, to estimate the target’s position simultaneously.