Abstract: A critical challenge to the commercialization of clean and high-efficiency solid oxide fuel cell (SOFC) technology is the insufficient stack lifespan caused by a variety of degradation mechanisms, which are associated with cell components and chemical feedstocks. Cell components related degradation refers to thermal/chemical/electrochemical deterioration of cell materials under operating conditions, whereas the latter regards impurities in feedstocks of oxidant (air) and reductant (fuel). This article provides a thermodynamic perspective on the understanding of the impurities-induced degradation mechanisms in SOFCs. The discussion focuses on using thermodynamic analysis to elucidate poisoning mechanisms in cathodes by impurity species such as Cr, CO₂, H₂O, and SO₂ and in the anode by species such as S (or H₂S), SiO₂, and P₂ (or PH₃). The author hopes the presented fundamental insights can provide a theoretical foundation for searching for better technical solutions to address the critical degradation challenges.