The invention relates to the technical field of ultra-short fiber, in particular to an ultra-short electrospinning polyimide nanofiber and a preparing method thereof. The preparing method of the ultra-short electrospinning polyimide nanofiber includes the steps of preparing a polyamide acid solution, conducting electrostatic spinning to form polyamide acid fiber felt, slitting the polyamide acid fiber felt into strips, conducting heat drawing to form high-orientation polyimide nanofiber bundles, and conducting cutting to form the ultra-short electrospinning polyimide nanofiber, wherein the width of the strips obtained by slitting the polyamide acid fiber felt is 3-8 cm, and the length of the ultra-short electrospinning polyimide nanofiber obtained through cutting is 0.1-2.00 mm. The ultra-short nanofiber even in length distribution can be prepared, and the nanofiber is quite high in dispersity and has potential applicability for preparing carbon fiber composites and flexible honeycombmaterials.