A method for rapid screening and qualitative and quantitative determination of three biguanides, MH, PH and BH, in Jiangtang capsules by reversed-phase ion-pair-LC-MS was established and validated. Anagilent technologies C18 column (4.6× 250 mm, 5 μm) was used for the determination at 235 nm. A methanol-B ammonium acetate solution (0.01 mol/L) was used as the mobile phase for gradient elution at a flow rate of 0.5 mL/min. After the HPLC detection, the mass spectrometer for positive ion mode scanning was used for screening. The recovery of standard addition was 87.5%~108.4%, and the relative standard deviation was 0.5%~7.4%, with good precision and accuracy.