A preparation method of a heat-not-burn cigarette paper with boron nitride as a thermally-conductive filler includes: mixing potassium oleate, polyvinyl alcohol (PVA) and water, thoroughly stirring under an ultrasonic condition, aging, and filtering until there is no precipitate; thoroughly mixing a resulting mixed solution with a softwood pulp and a hardwood pulp to obtain a coarse pulp; and under stirring, adding boron nitride and calcium carbonate as a filler to the coarse pulp, heating to 60° C., and stirring for thorough mixing to obtain a pulp for sizing and papermaking. The present disclosure effectively improves the stability of a cigarette paper by improving a coefficient of thermal conductivity of the paper. Boron nitride, when used as a thermally-conductive filler in a thin-walled or paper product, enables high heat removal capacity. The preparation method retains the original whiteness and transparency of the cigarette paper, and provides high conductivity.