［Objective］This study aimed to explore the effects of tillage practices on soil organic carbon loss/leaching process and their coupled synergistic mechanism in red soil slope farmland，and to provide a scientific basis for regulating soil organic carbon loss/leaching by optimizing tillage practices in red soil slope farmland. ［Methods］Four tillage practices were established，including plastic film mulching（PM），cross-slope ridge tillage（RT），downslope ridge tillage（DT）and conventional tillage（CT）. A refined indoor rainfall simulation experiment was conducted，and structural equation model（SEM）was employed to analyze the mechanism by which different tillage practices influence the process of soil organic carbon loss/leaching of the red soil slope farmland under the effect of rainfall erosion.［Results］The surface runoff and interflow under different tillage practices were ranked as PM>DT>CT>RT，and RT>CT>DT>PM，respectively. Among them，surface runoff accounted for 60.6%，34.9%，53.4% and 45.8% of the total runoff in PM，RT，DT and CT plots. The runoff form of PM and DT was mainly surface runoff，while the runoff form of RT and CT was mainly interflow. The runoff，sediment yield，and organic carbon loss/leaching were significantly affected by the interaction of tillage practices，crop growth stage，and rainfall intensity（p<0.01）. Among them，the total sediment yield of DT was the largest，which was 2.00-8.28 times higher than those of other tillage practices（p<0.05）. The soil organic carbon loss/leaching under different tillage practices and growth stages followed the order of DT>CT>PM>RT，and heading stage>flowering-grain stage>seedling stage. RT significantly reduced organic carbon loss/leaching by 4.9% to 52.8% compared to other tillage practices（p<0.05）. The loss/leaching of organic carbon through surface runoff，interflow，and eroded sediment accounted for 56.1%，18.1% and 25.8% of the total loss， respectively. SEM analysis showed that tillage practice and rainfall intensity indirectly affected soil organic carbon loss/leaching process by affecting surface runoff，interflow，and sediment yield. Among them，the influence of surface runoff was the greatest，followed by sediment yield and interflow.［Conclusion］Surface runoff and erosion sediment are the main ways of soil organic carbon loss/leaching in red soil slope farmland. RT has significant advantages in reducing surface runoff，sediment yield，and controlling soil organic carbon loss/leaching in red soil slope farmland，making it a preferable tillage practice for sustainable management of red soil slope farmland.