Abstract Base impedance has a direct effect on mechanical equipment’s properties, and thus its accurate measurement constitutes an important foundation for the evaluation of these properties. Through theoretical deduction and base impedance measurement, we investigated the influences of impact hammer parameters on mechanical impedance measurement using an impact excitation method. By comparing the effects of hammer head softness and hammer size on base’s mechanical impedance measurements, we know that soft and hard hammer heads were suitable for the impedance measurement in low and high frequency regions, respectively, and that hammer size had a little influence on impedance measurements.