Aging of oil-paper insulation systems in converter transformers directly threatens equipment safety and reliability. This study investigates the non-uniform life distribution of such insulation systems via electromagnetic-thermal-fluid multiphysics coupling analysis. First, a coupling model is developed to characterize temperature distributions within transformers under varying loads. Second, a temperature-aging mapping model is established to quantify relative aging rate distributions of oil-paper insulation. Finally, a life-state deduction model based on spatiotemporal aging rate variations is constructed to analyze life loss patterns in different temperature zones. Results show that winding hot-spot temperatures increase with load rates, and relative aging rates align with temperature field distributions. Notably, the upper winding regions exhibit significantly higher aging rates than edge areas under high loads. These findings provide critical insights for identifying insulation weak zones and designing differentiated maintenance strategies to optimize converter transformer reliability and lifespan management.