The invention relates to a preparation method of graphene solution phase. The method is characterized by comprising the following steps: (1) oxidizing graphite, (2) stripping mother liquid of the oxidized graphite, (3) reducing graphene oxide, wherein, polymer surface-active agent added into colloidal solution of graphene oxide is used as stabilizing agent and hydrazine hydrate is used as reducing agent. Compared with the prior art, the invention has the advantages that the obtained graphene has large area which can reach thousands or more square microns; the effective control of the sizes of graphene product can be realized only by selecting the size of the raw material of graphite, and the size of graphene can be effectively controlled between 20-200 microns; the concentration of the obtained graphene soliquid is high, which can be up to 5-10g / l, the stability of the graphene soliquid is good, and the graphene soliquid can not be subsided when being stewed for months; the method has the advantages of simple whole process, strong controllability and low price of adopted polymer surface active agent, thus being applicable to low-cost and large-scale production.