The invention discloses a preparation method of solid sodium polyacrylate. Graphene is added for ultrasonic dispersion, the graphene is evenly distributed in a solution, acrylic acid molecules also can be evenly dispersed on the surface of the graphene, sodium hydroxide, a chelating agent and an initiator are added in the following process, it can be guaranteed that a reaction is conducted on the surface of the graphene, various raw materials can be added at a time in the reaction process, repeated adding is not needed, the reaction time is shortened, the reaction efficiency is improved, and the conversion rate is increased; the prepared product is centralized in distribution of the molecular weight, and has a good effect when specifically used for printing and dyeing, papermaking and the like in the following process.