<p>Blade coating is widely employed in fabricating photoresist films due to its high efficiency, cost-effectiveness, and suitability for high-performance thin-film manufacturing. However, the blade straightness error significantly affects lateral (along-blade direction) thickness uniformity, thereby compromising device performance. While prior studies have predominantly investigated thickness uniformity along the blade-moving direction, the mechanisms underlying lateral uniformity remain inadequately understood. In this work, a systematic series of experiments was conducted to explore the influence of blade straightness error on lateral thickness uniformity. Experimental results demonstrated a nearly linear correlation, with greater blade straightness errors producing higher lateral non-uniformity. An empirical model linking blade straightness error to lateral uniformity was subsequently established, identifying a critical blade straightness error threshold of 20&#xa0;μm to maintain lateral non-uniformity below 5%. To elucidate the underlying mechanisms, a three-dimensional computational fluid dynamics (CFD) model based on the Navier–Stokes equations coupled with Fick’s law of mass transfer was developed. The simulations highlighted the complex interplay among viscosity, surface tension, solvent evaporation, and leveling dynamics. Additionally, a volatile liquid film leveling model was derived, explaining the influence of blade straightness error on film uniformity. Ultimately, a predictive model capable of quantitatively estimating lateral thickness uniformity in blade-coated photoresist films was proposed, providing critical insights for process optimization.</p>