The invention provides a preparation method of high-conductivity graphene powder. The preparation method comprises the following steps: S1, dispersing raw material level graphite in a mixed solution containing an intercalator and an oxidizing agent, and performing uniform stirring so as to obtain a new solution; S2, placing the new solution in a pressure vessel, introducing inert gas, and performing pressure maintaining and stirring; S3, performing purification operation so as to extract an upper layer intercalator, and stripping out a single-layer oxidized graphene solution from lower-layer products in a mechanical manner; S4, performing drying treatment through a powder drying technology, and then dissolving the single-layer oxidized graphene powder in a solvent again so as to form a low-concentration single-layer oxidized graphene solution; S5, adding a reducing agent, and performing a stirring reaction at 0-50 DEG C for a certain time so as to obtain a single-layer graphene solution; S6, performing drying treatment and heat treatment on the single-layer graphene solution according to the powder drying technology so as to obtain the high-conductivity graphene powder. The preparation method disclosed by the invention has the advantages that the prepared graphene has few structural defects and is good in conductivity and high in yield; the preparation process is simple and convenient to operate, the cost is low, and the large-scale production is easy to realize.