Abstract: According to the prescribed amount, the Xuanfei Baidu formula was prepared. After boiling with flamming fire, the mixture was simmered for 60 min, passed through gauze, and concentrated its volume up to 400 mL by soft fire. The mixture was passed through filter paper and 0.45 μm water filter membrane. The test solution of Xuanfei Baidu formula was separated on Agela Promosil C₁₈ chromatographic column, using the mixed solution composed of 0.1% (volume fraction) phosphoric acid solution and methanol at different volume ratios as mobile phase for gradient elution at 30 ℃ of column temperature. The components of the test solution were detected at wavelength of 220 nm, and the chromatogram was recorded. High performance liquid chromatography (HPLC) fingerprint of Xuanfei Baidu formula was established according to the Similarity Evaluation System for Chromatographic Fingerprint of Traditional Chinese Medicine (2004 A Edition). As shown by the results, there were 24 common peaks in the fingerprints of 11 batches of Xuanfei Baidu formula. Compared with the emodin reference substance, the compound of No.24 peak was confirmed to be emodin, and the similarity was in the range of 0.988-1.000 between fingerprints of 11 batches of Xuanfei Baidu formula and reference fingerprint.