Although quality control is critical in clinical research to ensure reliable data collection, few observational studies have a data quality control system. To improve the quality of a multicenter observational study including patients with hepatitis C virus-associated cirrhotic receiving antiviral therapy, we assigned a quality control officer to the study office to examine query content. A total of 369 patients were enrolled from 2019 to 2021, and data collection management was conducted by the Research Electronic Data Capture system, with regular entry promotion and data checks. The 847 queries that occurred between 2020 and 2021 were categorized into "not entered" (617 queries) and "data-related" (230 queries), and all queries were resolved. The semi-annual changes in query content showed a decreasing trend for "not entered" (212/179/133/93), while "data-related" remained (34/54/86/56). Our findings demonstrated that the assignment of a quality control officer could enhance data quality, leading to improved quality of observational studies.