Objective To investigate the changes in the diagnostic and therapeutic methods for Lemmel's syndrome over the past 20 years in China, and to provide experience for standardized diagnosis and treatment of this disease. Methods A retrospective analysis was performed for the clinical data of 23 patients with Lemmel's syndrome who were diagnosed and treated in Tongji Hospital of Tongji University from January 1998 to June 2017 and 384 patients with Lemmel's syndrome reported in China during the same period of time ( 407 patients in total) .According to the admission time, the patients were divided into groups A ( 139 patients admitted from 1998 to 2007) and B ( 268 patients admitted from 2008 to 2017) . The patients' clinical features, diagnostic and therapeutic methods, and prognosis were recorded. The t-test was used for comparison of normally distributed continuous data between groups, and the Wilcoxon rank sum test was used for comparison of non-normally distributed continuous data between groups; the chi-square test was used for comparison of categorical data between groups.Results Compared with group A, group B had significantly higher age of onset ( 67. 8 ± 17. 8 vs 62. 3 ± 12. 3, t =-13. 238, P = 0. 019) and incidence rate of cholangitis ( 45. 9% vs 32. 4%, χ2= 6. 903, P = 0. 009) . As for diagnostic methods, compared with group A, group B had a significantly higher proportion of patients who used multi-slice spiral CT ( MSCT) ( 26. 9% vs 8. 6%, χ2= 18. 576, P < 0. 001) , endoscopic ultrasonography ( EUS) ( 15. 7% vs 5. 8%, χ2= 8. 352, P = 0. 004) , magnetic resonance cholangiopancreatography ( MRCP) ( 75. 0% vs 33. 1%, χ2= 67. 303, P < 0. 001) , or endoscopic retrograde cholangiopancreatography ( ERCP) ( 63. 4% vs 36. 7%, χ2=26. 377, P < 0. 001) , while the two groups had a similar false positive rate ( 22. 8% vs 28. 1%, χ2= 1. 385, P = 0. 239) . As for therapeutic methods, compared with group A, group B had a significantly higher proportion of patients who underwent ERCP combined with conservative pharmacotherapy and surgical operation ( χ2= 34. 758, P < 0. 001) . There was a significant difference in recurrence rate between endoscopic surgery group and conservative pharmacotherapy group ( χ2= 40. 211, P < 0. 001) , as well as between surgical operation group and conservative pharmacotherapy group ( χ2= 26. 785, P < 0. 001) ; there was no significant difference in recurrence rate between surgical operation group and endoscopic surgery group ( χ2= 0. 055, P = 0. 815) , but endoscopic surgery had the advantages of minimal invasiveness, fast recovery, and low costs. Conclusion Age of onset of Lemmel's syndrome is gradually increasing. MSCT, EUS, MRCP, and ERCP applied alone or in combination are major diagnostic methods, and ERCP is the preferred therapeutic method for Lemmel's syndrome.