The invention belongs to the field of modified carbon felt production, and especially relates to a preparation method of a graphene modified carbon felt. For the problems of long preparation time andlow efficiency of the existing graphene-modified carbon felt, the following scheme is proposed, and the preparation method comprises the following steps of step S1, preparing a placing rack, mounting10 to 20 grating plates on the placing rack, wherein the distance between the upper and lower grating plates is 2 to 16 mm, placing the carbon felt on the grating plates, and putting a shelf into an acid solution for soaking; step S2, stirring the acid solution while soaking, enabling the acid solution to impact the carbon felt, accelerating the soaking speed, and cleaning sundries floating on thesurface of the acid solution while stirring; step S3, cleaning and drying the carbon felt after soaking, and then heating; and step S4, after heating, taking out the carbon felt, and cooling to roomtemperature to obtain the grapheme-modified carbon felt. The preparation method of the graphene-modified carbon felt provided by the invention can effectively shorten the preparation time of the graphene-modified carbon felt, and improve the preparation efficiency.