Proton exchange membrane water electrolyzers (PEMWEs) are a promising technology for large-scale hydrogen production, yet their industrial deployment is hindered by the harsh acidic conditions and sluggish oxygen evolution reaction (OER) kinetics. This review provides a comprehensive analysis of recent advances in iridium-based electrocatalysts (IBEs), emphasizing novel optimization strategies to enhance both catalytic activity and durability. Specifically, we critically examine the mechanistic insights into OER under acidic conditions, revealing key degradation pathways of Ir species. We further highlight innovative approaches for IBE design, including (i) morphology and support engineering to improve stability, (ii) structure and phase modulation to enhance catalytic efficiency, and (iii) electronic structure tuning for optimizing interactions with reaction intermediates. Additionally, we assess emerging electrode engineering strategies and explore the potential of non-precious metal-based alternatives. Finally, we propose future research directions, focusing on rational catalyst design, mechanistic clarity, and scalable fabrication for industrial applications. By integrating these insights, this review provides a strategic framework for advancing PEMWE technology through highly efficient and durable OER catalysts.In order to realize the efficient application of the industrial PEMWEs, material design strategies for stimulating the activity and stability capability of OER electrocatalysts are summarized, including (i) morphology/support effects, (ii) structure/phase engineering, (iii) electronic configuration/interaction. Furthermore, the reaction mechanism is deeply clarified, and electrode engineering and challenges of IBEs in practical PEMWE application are focused.