The invention provides a hydrothermal preparation method of a graphene-coated sulfur/porous carbon composite material and relates to a preparation method of the graphene-coated sulfur/porous carbon composite material for a positive electrode material of a lithium-sulfur storage battery. The hydrothermal preparation method is used for solving the technical problem that the electrochemical property of the positive electrode material of an existing lithium-sulfur battery, namely a graphene-coated sulfur-containing composite material, is low. The hydrothermal preparation method comprises the steps of mixing and scattering the sulfur/porous carbon composite material with graphene slurry or oxidized graphene slurry, carrying out hydrothermal synthesis to prepare a hydrogel column, and drying to obtain the graphene-coated sulfur/porous carbon composite material. According to the graphene-coated sulfur/porous carbon composite material prepared by utilizing the hydrothermal preparation method, the outer surfaces of the graphene sheet layers are coated with sulfur/porous carbon composite material particles, a graphene conduction network is generated among the particles, and the obtained graphene-coated sulfur/porous carbon composite material is in a hierarchical core-shell structure; the positive electrode material has the high specific capacity, the long cycle life and the good rate capability; the composite positive electrode material can be used as a positive electrode material in a lithium secondary battery.