Objective To establish and verify a liquid chromatography-mass spectrometry (LC-MS) method for the determination of 3 residual chloramphenicols in the urine of pregnant women.Methods Urine was purified and concentrated by Oasis HLB solid phase extraction column, and liquid phase separation was performed on a SHISEIDO MG-C₁₈ (100 mm× 3.0 mm, 3.0 μm) column with mobile phase of acetonitrile-water (containing 0.1% formic acid) for gradient elution. Electrospray ionization source was used for MS, and ion monitoring mode was selected for detection ［M-H］^-: chloramphenicol m/z 320.8, florfenicol m/z 355.8, thiamphnicol m/z 353.8, and sulfonamide (internal standard) m/z 268.9. Results The 3 residual chloramphenicols in urine showed a good linear relationship in the range of 5-500 ng/mL (all r＞0.999); the precision and accuracy within and between batches were good (relative standard deviation＜8.9%, ∣relative error ［RE］∣＜9.3%); the extraction recoveries ranged from 71.4% to 108.5%, with good stability (∣RE∣＜11.8%), almost with no residue; dilution did not affect the precision and accuracy of the determination. A total of 18 urine samples from pregnant women of different trimesters (first trimester, second trimester, and third trimester) were tested, chloramphenicol was detected in most of the samples (but the concentration was below the minimum quantitation limit of 5 ng/mL), florfenicol was detected in a few samples, and no thiamphnicol residue was detected at all. Conclusion The present method is simple, reproducible and suitable for the determination of 3 kinds of chloramphenicols in urine. It can provide a methodological basis for the study of the correlation between chloramphenicol residues and adverse pregnancy outcomes of pregnant women.