The objective of this paper was to prepare self-emulsifying drug delivery systems of genistein.Through drawing pseudo-ternary phase diagrams and evaluating self-emulsification efficiency, the optimum formulation was obtained for genistein.RP-HPLC was used to determine the content of genistein.In the optimum formulation, Et oleate, T5C5 (50% Tween 80-50% Cremophor EL35) and 1,2-propanediol were selected as oil phase, emulsifier and cosolvent, resp., with the proportion of 45:45:10.The content of genistein was fixed at 10% (weight/weight) of the vehicle.The SEDDS of genistein was prepared, which was suitable to prepare soft capsules.