The invention provides a method, which comprises the following steps of providing fluorine-containing high molecular dispersion liquid (A) and aromatic diamine (B) dissolved in a first solvent (C), wherein the fluorine-containing high molecular dispersion liquid (A) contains fluorine-containing high molecular polymers (a-1), a second solvent (a-2) and dispersing agents (a-3); mixing the fluorine-containing high molecular dispersion liquid (A) and aromatic diamine (B) to form a first mixture; adding aromatic tetracarboxylic dianhydride (D) into the first mixture so as to form a polyamide acid solution; performing the solvent removal step and the heating step on the polyamide acid solution so as to prepare the polyimide. The prepared polyimide film has a low dielectric coefficient and a low loss factor.