AbstractThe utilization of accelerators has been a common approach to prepare low‐temperature curable polyimide (PI). However, the accelerators have gradually fallen out of favor because of their excessive dosages and negative effect on the properties of PI. In this work, a new strategy of introducing accelerators by grafting to eliminate these disadvantages is presented. A novel quinoline derivative named 6‐([1,1′‐biphenyl]−4‐yl)−4‐chloroquinoline (NQL) is designed for this purpose, and an ultralow dosage of only 2.5 mol% is sufficient to prepare low‐temperature curable PI. The favorable low‐temperature curing effect of NQL is attributed to its strong alkalinity (pKa = 18.47) and electron‐donating ability. At a curing temperature of 200 °C, the PI with 2.5 mol% NQL showed outstanding properties (Young's modulus of 5.73 GPa, elongation of 37.3%, tensile strength of 237 MPa, and coefficient of thermal expansion of 16 ppm K⁻¹). In particular, NQL can even lower the curing temperature to 180 °C and the ultralow temperature curable PI film still retains excellent properties. These results demonstrate that introducing low‐temperature curable accelerators by partial grafting instead of blending is a promising way to furnish low‐temperature curable PI, and provide insights into the preparation of polyimide with high performance in advanced packaging.