Protein crystal nucleation processes are drawing increasing interests in both academic and industrial communities. Electric held is a promising means, due to its versatility and easy application, among various external fields that may lead to controllable desired protein crystal nucleation. Different from literature reported experimental and theoretical studies that examined the effects of high frequency electric fields; this work was focused on the low frequency range. For this purpose, Hen-White Lysozyme crystal nucleation from its aqueous solution was used as the model system. We found by experiments that the nucleation rate is non-monotonously dependent on electric field frequency less than 1 kHz, which may be ascribed to the mutual orientation modification between neighbor protein molecules induced by the external low frequency, and is different from the case of high frequencies that influence the intermolecular interactions. (C). 2015 Elsevier B.V. All rights reserved.