Wavelet transform is applied to abstract of the characteristic points of CAP. A new method has been developed for detecting the start point(u) ascending branch of CAP, and Dicrotic Notch(DN) descent branch on CAP. It is discussed that the principle of the signal's singularity detectiom with wavelet transform modulus maxima points and zerocrossing points. The method is proposed to detect point u using the slope of smoothing signal at inflection point. By this method, we can achieve accurate detection result, even under serious baseline drift and strong noise.