Polymer materials with a wide range of applicable temperatures, excellent dielectric properties, and high reliability under complex operating conditions are imperative for packaging applications of next-generation power devices. However, conventional polyimides (PI) typically require thermal imidization at higher temperatures, which inevitably causes irreversible damage to the solder and other components. To this end, this article proposes a feasible strategy that involves the introduction of low-temperature catalyst-modified nanofillers into polyamic acid. This approach utilizes the nucleophilic attack behavior of the catalyst along with the stacking effect of polymer segments to construct ordered, stable, and high-performance polyimide composite networks at low temperatures. The catalyst aminoquinoline (AQL) compensated for the unformed polymer network at low temperatures, while rectorite (REC) nanosheets restricted the molecular chain movement and improved the PI electro-thermal properties. The results show that with the addition of only 3.0 wt.% of QL-REC, the PI composites can achieve 97.5% imidization at 190 °C and possess low dielectric constant (3.2@1 MHz), matched thermal expansion coefficient (24.4 ppm·°C⁻¹) and high breakdown strength (361.9 kV·mm⁻¹). Furthermore, the comprehensive nature of the PI composites enables them to meet the packaging requirements for SiC-oriented devices. This work provides new inspiration for the development of polymeric materials for advanced electronic packaging applications.