Objective:To compare the assay and related substance detection methods of erythromycin lactobionate in the Chinese Pharmacopoeia 2020(ChP),USP 2023(USP),JP18(JP),BP2023(BP)and EP 11.0(EP),investigate the differences between the test results obtained from 7 batches of erythromycin lactobionate for injection samples by using ChP and BP methods and thus provide a reference for the improvement of specification of erythromycin lactobionate.Methods:The differences of test methods and limits under the items of assay and related substances of erythromycin lactobionate in the above five pharmacopoeias were listed and compared.The related substances and contents of erythromycin lactobionate for injection samples from different manufactures were tested with methods stated in ChP and BP,and then compared and analyzed.Results:The items of related substances were determined by high performance liquid chromotographic methods in the ChP,EP and BP.The test methods and limits in the EP and BP were the same,which were different from that in ChP.The related substances were not determined in the USP and JP.There are obvious differences between the chromatographic methods and limits for the items of related substances in the ChP and BP,i.e.,BP contains 7 specific impuri-ties,while ChP contains only 2 specific impurities.The limits for any other impurity and the total amount of impurities were lower in the BP than those in the ChP.The antibiotic microbiological assay was used as the test method for the item of assay in the ChP,USP and JP based on different bacterial strains,which was different from the chromatographic method used in the BP.Based on the different methods of the ChP and BP,the related substances and content determination results of 7 batches of erythromycin lactobionate for injection samples met the acceptance criteria.The detection efficiency of BP related substances inspection method for specific impurities and total impurities were significantly higher than that of the ChP method.Conclusion:The BP method is superi-or to the ChP method in the detection of erythromycin lactobionate and erythromycin lactobionate for injection related substances.In terms of content determination,the external standard method adopted by BP is feasible to replace the antibiotic microbiological assay adopted by the ChP.Related substances and content determination methods adopted by the BP can provide an important reference for the revision and improvement of erythromycin lactobionate standard in the ChP.