The fluctuation in heart rate (HR) has been widely employed for observing autonomic modulation. Compared to ECG used in clinic， a standard pulse oximeter (Sp02) was often used in home or during exercise to measure the fluctuation of their heart rates. However， precise extraction of HR was usually interfered by the movements of fingers and toes or poor connection of probes. In this paper， we discuss both moving-average method and wavelet method to extract heart rate information from raw plethysmograph waveform. Results from these two methods were compared. Our results indicated that 6-level of multi-resolution analysis obtained from wavelet transform can effectively extract the HR in comparison to that of moving average approach