The ECG (Electrocardiogram) signal reflects the electrical activity of the heart. Since amplitude of ECG signal is of order of few mV, it is susceptible to many types of noises and amongst which the most disturbing is power line interference (PLI). Variations in frequency of PLI further complicate the problem which can be taken care by implementation of adaptive notch filter (ANF). ANF normally requires a reference input which is not possible in all cases. In this paper, we have proposed an intelligent adaptive filter which does not require a reference input. Proposed method first detects the frequency of PLI noise then adaptively tracks and eliminates PLI from ECG signal.