The invention discloses a preparation method of modified superfine graphene. The preparation method includes the following steps that (1), graphene is subjected to grinding, specifically, the grapheme is placed in a grinder and is ground to obtain graphene pasty material; (2), the graphene pasty material is subjected to stage treatment, specifically, the graphene pasty material is put into a high-speed centrifugal settling type grader, the graphene pasty material whose particle diameter is less than or equal to 1 [mu]m is concentrated in the middle of the grader, and is stored in a storage tank after being led out; and (3), the graphene pasty material whose particle diameter is less than or equal to 1 [mu]m is subjected to kneading treatment, specifically, the graphene pasty material whose particle diameter is less than or equal to 1 [mu]m is put into a kneading reaction device, a surface treating agent is added, the kneading treatment is conducted, the superfine graphene is obtained after being kneaded, and in the period, the accumulating density of superfine graphene powder is controlled within 0.5-1.2. According to the preparation method, the prepared modified superfine graphene particles have the characteristics of being good in dispersing performance, low in accumulating density and the like. Partial shielding and disturbing to electromagnetic waves and wireless signals are achieved, and the effect of gaining advantages in information competition is realized.