Objective: To establish a HPLC method to determine the entrapment efficiency (EE) and drug loading (DL) of biochanin A loaded solid lipid nanoparticles (BCA-SLN) and biochanin A loaded nanostructured lipid carriers (BCA-NLC). The distinction between the two kinds of nanoparticles in EE and DL was investigated. Method: Centrifugation ultrafiltration method was used to isolate the free drug. The content of drug was determined by HPLC. The analytical column was Cosmosil C18(4.6 mm×250 mm

5 μm) and column temperature was at 30℃. The mobile phase was acetonitrile-0.1% phosphoric acid (60: 40). The flow rate was 1 mL·min-1. The UV detecting wavelength was set at 260 nm. Result: BCA was linear in the range of 0.005-5.000 g ·L-1 (r=1.000). The EE and DL of BCA-SLN were (97.15±0.28)% and (6.38±0.043)%

respectively. The EE and DL of BCA-NLC were (99.57±0.11)% and (6.91±0.044)%

respectively. There was significant difference between two kinds of nanoparticles in EE (P≤0.05)and DL (P≤0.05). Conclusion: HPLC combined with centrifugation ultrafiltration method to determine the EE and DL of BCA-SLN/BCA-NLC is accurate and efficient. The EE and DL of NLC are higher than SLN.