Disclosed is a daidzein derivative as represented by formula (I), or pharmaceutically acceptable salt thereof. Compared to the daidzein in the prior art, the daidzein derivative hydrochloride, in particular to the 7-O-N,N-diethyl-aminoacetyl daidzein hydrochloride, prepared by the daidzein derivative of the present invention, has better solubility and effect for treating cardiovascular diseases.