disclosed is a daidzein derivative as represented by formula , 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 .