<p>Flexible perovskite solar cells (FPSCs) have demonstrated considerable potential as a next-generation photovoltaic technology for space applications. However, their performance stability in space radiation environments remains a critical challenge. This paper proposes a performance evaluation strategy for FPSCs subjected to space irradiation damage. This strategy integrates a radiation damage model with a multi-physics field-coupled optoelectronic device performance simulation methodology, systematically assessing the protective efficacy of four commonly utilized polymer encapsulants under low Earth orbit proton radiation exposure. The results show that polyimide (PI) is better at blocking protons at all energy levels, making it the best encapsulation material for FPSCs. Furthermore, COMSOL fitting calculations reveal that PI-encapsulated devices exhibit sustained high performance following radiation exposure, underscoring their remarkable stability in terms of optoelectronic performance. This study provides a robust theoretical foundation and technical support for the protective design of spacecraft components and serves as a significant reference for the selection of appropriate encapsulation materials for future space applications.</p>