Objective: Determination of aristolochic acid in Longdanxiegan pilis by TLCS. Method: Dual wave-length refleclion zigzag scanning was performed; λs =395 nm, λR =500 nm; slit width; 0.4 mm × 0. 4 mm; linear parameter: SX=3; developing solvent; benzene - methanol - acetic acid 36% (17: 2:0.2). Results: The Standard curve for aristolochic acid was linear in the range 0. 9 - 4. 5 μg (r = 0. 999 8 ). The average recovery is 96. 78% (n =6). Conclusion: This method is accurate with good recovery.