Abstract: In order to clarify the distribution characteristics of in−situ stress in fault−controlled fracture−vug reservoirs and improve the exploration efficiency and development benefits of carbonate reservoir. Based on geological information, drilling information, seismic data, and seismic attribute analysis, this article conducts a modeling of the in situ stress field in the FY210 fault zone of the Fuman Oilfield, clarifies its in situ stress distribution mode, analyzes the effectiveness of fracture mechanics, and proposes a reservoir quality evaluation method and production improvement strategy based on in situ stress analysis. The results indicate that: ① the heterogeneity of fault−controlled fracture−vug reservoirs is strong, and faults, fractures, and pores cause abnormal changes in local stress fields. The in situ stress field of the cave body shows a "shell like" distribution feature, and the external strong stress shell shows stress concentration. The low value area inside is a favorable reservoir body, and the development of fractures, pores, and caves can be inferred based on the changes of in situ stress. ② High stress areas are unfavorable drilling targets, and reservoirs with high stress characteristics have poor permeability. During drilling, wellbore collapse may occur, and such areas should be avoided through large−scale renovation, deepening, or lateral drilling. ③ In addition to conventional petrophysical parameters, geomechanical properties such as in−situ stress, fracture activity, and fracturability are also important factors that affect the quality and productivity of fracture−controlled vuggy carbonate reservoirs. Well placement and well trajectory optimization should fully consider factors related to in−situ stress, while also taking into account reservoir reconstruction efficiency to promote single well production and reservoir benefit development.