The Luzhou Block in southern Sichuan Basin is an important shale gas production area in China, where the Wufeng-Longmaxi Formation shale gas resources are abundant, indicating a high exploration and development potential. The present-day in-situ stress has important applications in the analysis of shale gas migration and enrichment, drilling and completion engineering, reservoir fracturing and well pattern deployment, etc. The present-day in-situ stress state of Wufeng-Longmaxi Formation deep shale gas reservoirs in the Luzhou block was analyzed, and natural fracture activity and hydraulic fracture propagation under the effect of present-day in-situ stresses were discussed. The research results show that the dominant present-day in-situ stress orientation in the Wufeng-Longmaxi Formation shale gas reservoir is WNW-ESE-trending. The magnitude of horizontal maximum principal stress is the largest, magnitude of horizontal minimum principal stress is the lowest, indicating a strike-slip stress regime. The stress difference in the Wufeng Formation and S₁ l^1-1-1 layer is 11.90 ~ 15.76 MPa and 11.80 ~ 16.75 MPa, respectively, which is beneficial for generating complex fracture networks. Under the present-day in-situ stress conditions, natural fracture activity in the Wufeng-Longmaxi Formation shale gas reservoirs of Luzhou Block is relatively weak. With fluid injection during shale gas development, natural fractures are gradually activated, and their critical pressure increase is 15 ~ 23 MPa. Hydraulic fractures vertically propagate under the strike-slip stress regime. The results can provide present-day in-situ stress analysis basis for further beneficial development of deep shale gas in the Luzhou Block of southern Sichuan Basin.