Abstract: In order to obtain the optimum extraction conditions for flavoness from Semen Astragali Complanati, on the basis of one-factor experiment, the ratio of solvent-to-sample, ultrasonic extraction temperature, particle size and ultrasonic extraction time were optimized by response surface methodology (RSM) and the absorption of extracts for flavones was chosen as the response.The results showed as follows:the maximum absorbance wavelength for the flavones extracts was 323nm, the suitable extractant was 60% acetone, the particle size was 120 mesh, the ultrasonic extraction temperature was 50℃, the ultrasonic extraction time was 60min, and the ratio of solvent-to-sample was 40:1 (mL/g) .Under these conditions, the crude yield was 16.19%.The morphology for the particles was studied by scanned electron microscopy, many honey-combed microstructures appeared, and hence facilitated the mass transfer and promoted extraction efficiency.