In order to extract the vibration value which indicates the same frequency as rotating speed from the lower S/N ratio signal and adapts to speed variety, the method of Narrowband Tracking Filtering was deduced by the principle of correlation analysis. Based on this method a Narrowband Tracking Filter was designed and implemented by Multiplying Digital-to-Analog Converter (MDAC). The experimental results demonstrate that the filter has the good performance and is able to meet the requirements of dynamic balancing measurement, which the relative error of amplification is better than 0.2%, the absolute error of phase is better than 0.4° and its output can track the change of rotating speed when the variety ratio of speed is under 9000r/min².