Dynamic spectrum method extracts the absorbance of the artery pulse blood with some wavelengths. The method can reduce some influence such as measurement condition, individual difference and spectrum overlap. It is a new way for noninvasive blood components detection. However, how to choose a dynamic spectrum extraction method is one of the key links for the weak ingredient spectrum signal. Now there are two methods to extract the dynamic spectral signal—frequency domain analysis and single-trial estimation in time domain. In the present research, comparison analysis and research on the two methods were carrued out completely. Theoretical analysis and experimental results show that the two methods extract the dynamic spectrum from different angles. But they are the same in essence—the basic principle of dynamic spectrum, the signal statistical and average properties. With the pulse wave of relative stable period and amplitude, high precision dynamic spectrum can be obtained by the two methods. With the unstable pulse wave due to the influence of finger shake and contact-pressure change, the dynamic spectrum extracted by single-trial estimation is more accurate than the one by frequecy domain analysis.