||In this work, aromatic soluble polyimide (PI) is presented as an alternative to low-temperature processable gate dielectric layers. Low-temperature processability of soluble PI is demonstrated by comparing dielectric and electrical properties with conventional PI at various annealing temperatures. The chemical structure effects of aromatic dianhydride and diamine monomers on device performance are then systematically investigated by evaluating four soluble PIs, in which monomeric precursors containing different backbones, side groups, and linkages. The results indicate that based on 4,4'-(hexafluoroisopropylidene)diphthalic anhydride soluble PI is the most promising gate dielectric candidate due to its high field-effect mobility, near-zero threshold electric-field, and excellent electrical stability. This work presents a step forward to the development of soluble PI gate dielectrics for flexible electronic devices with high device performance.