Abstract: OBJECTIVE To explore the solution of false positive in the detection of aflatoxin in Cassiae Semen. METHODS The impurities were eluted with 1% Tween-20 PBS solution, purified by immunoaffinity column and determined by photochemical derivatization after HPLC. The medicinal materials of Corydalis Rhizoma were compared and verified by HPLC-MS/MS. RESULTS The solution could effectively remove the interference of false positive components in Cassiae Semen, and could remove the colored components in Corydalis Rhizoma samples, and did not affect the retention of aflatoxin in immune affinity column. CONCLUSION The method is simple, stable and reliable. It can be used for the pretreatment of complex matrix samples, eliminate the interference of false positive. It can be used as a solution to the false positive in the determination of aflatoxin.