Pulmonary artery pressure is an important parameter for clinical diagnosis and physiological research. It used to be measured by the traditional invasive method, cardiac catheterization. A non-invasive method based on audio pulsed-wave Doppler signal and ECG is presented and the noninvasive evaluation system is developed. The key techniques, animal experiment and clinical probation are described in this paper. The key techniques include： wavelet de-noising, new percentile method as well as locating characteristic point with wavelet. According to the data obtained from animal experiments of 9 dogs and 60 cases, the relativity with cardiac catheterization exceeds 80% .