A supercritical CO2 fluid extraction (SFE) method was developed to extract isoflavone. A uniform design was used to investigate the effect of the extraction pressure, extraction time, extraction temperature, and medicinal materials granularity on isoflavone extraction efficiency. The optimum conditions of extraction were as follows: 45 MPa extraction pressure, 50 ℃ extraction temperature, 4 h extraction time, 40 eyes medicinal materials granularity, and the extraction efficiency was (0.361±0.012)%.