The invention discloses a refinement method of vitamin C sodium salt, belonging to the technical field of preparation of vitamin C sodium salt. The method comprises the following steps: (1) dissolving a vitamin C sodium salt crude product in water (the mass ratio of the crude product to water is 1:(1-4)), adding activated carbon which accounts for 1-1.5 wt% of the crude product, and filtering the mixed solution; (2) pressurizing the filtrate into a crystallizing kettle, adding methanol (which is 2-5 times by mass of the crude product) at 45-60 DEG C under the vacuum degree of -0.08 to -0.1 MPa, stirring to crystallize, cooling to 1-10 DEG C, and continuing stirring to crystallize; and (3) filtering the mixed solution obtained by the step (2), washing the filter residue with methanol, carrying out vacuum filtration, and drying the filter residue to obtain the vitamin C sodium salt crystal. The vitamin C sodium salt solution is crystallized under vacuum conditions to obtain the product with uniform particles; and thus, the method enhances the product quality and yield, lowers the production cost, and creates favorable economic benefit.