Abstract： Objective： To investigate the medication patterns used by OUYANG Yonghong in treating chronic atrophic gastritis （CAG） with liver qi stagnation and spleen deficiency syndrome using data mining techniques. Methods：Medical records of patients with CAG who were effectively treated by OUYANG Yonghong between February 1，2023，and July 31，2024，were collected. Data from these records were analyzed using the Ancient and Modern Medical Case Cloud Platform，SPSS Modeler 18.0，SPSS Statistics 26.0，and Excel 2016 to determine the frequency of use of Chinese medicines， their properties， flavors， and meridian tropism. Association rule analysis， complex network analysis，and cluster analysis were also performed. Results：A total of 313 medical records of patients with CAG with liver qi stagnation and spleen deficiency syndrome were included in this study， involving 161 Chinese medicines with a total frequency of 5 519 times. Among them，32 medicines with a frequency of ≥0.7%（high-frequency medicines）were identified. The top three properties were warm，neutral，and slightly cold，while the top three flavors were sweet， bitter， and pungent. The top four meridians were spleen， lung， stomach， and liver. Association rule analysis of high-frequency medicines identified three core medicine pairs， complex network analysis identified eight core medicines， and cluster analysis yielded six clustered prescriptions， with the core clustered prescription being： Codonopsis Radix，Citri Sarcodactylis Fructus，Cyperi Rhizoma，Perillae Caulis，Bupleuri Radix，Curcumae Radix， Amomi Fructus， and Aurantii Fructus Immaturus. Conclusion： Based on data mining techniques， this study investigated the medication patterns used by OUYANG Yonghong in treating CAG with liver qi stagnation and spleen deficiency syndrome. The basic therapeutic principle is to tonify the spleen and soothe the liver， supplemented by phlegm-dissipating and mass-dispelling， heat-clearing and detoxifying， and blood-activating and collateralsunblocking when phlegm-turbidity，heat-toxin，and blood stasis are present.