In high voltage testing the residual inductance of the test circuit or the stray capacitance of the test subject disturbs the standard lightning impulse with superimposed overshoot or oscillations on the front or tail of the waveform. This paper presents a new technique based on ESPRIT method for estimating the mean curve of HV lightning and switching impulse waveforms required by IEC 60 and IEEE Std. 4. ESPRIT analysis method is applied to analytical lightning impulses to estimate the mean curve of the lightning impulse using a bi-exponential model after removing high frequency components from the simulated impulse. The effectiveness of the method is assessed by conducting several cases of impulse waveforms including standard lightning and switching impulses, lightning impulses with front and tail oscillations, and lightning impulse with overshoot. The simulation results indicate the effectiveness and reliability of the proposed method. The results also show that ESPRIT is very useful and applicable tool for accurate estimates of the impulse mean curve and parameters (peak value, front time, and time-to-half-value).