The SU-8 thick photoresist lithography process is widely used in the preparation of high-aspect-ratio structures；however，the photoresist stripping process is prone to thickness fluctuations at different positions on the chip and between different chips，resulting in local over-or underexposure and reduced pattern transfer accuracy. This study employed the Taguchi method to investigate the effects of photoresist thickness and exposure dose on the lithography process under different prebake times. It was found that increasing the prebake time could effectively suppress line-width fluctuations. When the prebake time was increased from 90 to 110 min，the stability of the line width was improved by 86. 8%. Simulation analysis was conducted to investigate the mechanism of fluctuation suppression，and the results showed that extending the prebake time could effectively suppress the production of photoacid at the bottom of the SU-8 layer，increasing the concentration difference of the photoacid in the thickness direction，thereby reducing the amount of photoacid diffused to the unexposed areas on both sides during postbake and suppressing the line width changes caused by the mismatch between photoresist thickness and exposure dose. This provides a solution and theoretical reference for addressing the errors caused by fluctuations in the thickness of thick photoresist layers.