The present invention relates to an erythrocyte duoparental depressor factor (EDDF), its preparation method and application. Its preparation method includes the following steps: using human blood and adopting centrifugal separation process to obtain erythrocyte, using deionized water to hemolyze erythrocyte, after the hemolysate is stood still at 4 deg.C, heating the hemolysate at water bath with 100 deg.C, then cooling in ice bath, centrifugalizing obtained product more than 12000g at 4 deg.C to take supernatant, ultrafiltering supernatant to collect the ultrafiltrate whose molecular weight is less than 500D, freeze-drying said ultrafiltrate, making the freeze-dried sample undergo the process of column chromatograph for sorting and separation so as to obtain the invented product which can be used for preparing medicine for curing hypertension disease. |