At present, in the market, more than 85% of the electronic sphygmomanometers adopt oscillometric method to measure blood pressure. The key step of oscillometric method is to extract the pure oscillation pulse wave from the original signals, which is used for the measurement of blood pressure. This paper will use the self-made device based on the flation of blood pressure data acquisition to collect data. In the view of the high frequency noise and baseline drifting caused by the motor oscillation, respiration and body movement, electronic component temperature changes and so on, method of combination of moving average filter and mathematical morphology is proposed. The experimental result shows that this method can effectively eliminate the high frequency noise and drift signal in the oscillation pulse wave. The signal spectrum analysis shows that it clearly reduces the amplitude of high frequency signal, makes the SNR get a good improvement, and improves the accuracy of blood pressure measurement.