Preparation method of sugar

The invention provides a preparation method of sugar. The method comprises the following steps: decolorizing raw sugar syrup to obtain decolorized syrup; conveying a first part of the decolorized syrup into a crystallizing tank; the decolorized syrup is concentrated in the crystallizing tank, and a mixture of granular sugar and mother liquor is separated out; separating the mixture into granular sugar and molasses, and cleaning the granular sugar to obtain white granulated sugar; and conveying the molasses to an original liquid sugar production line, mixing the molasses with the second part of decolorized syrup conveyed to the liquid sugar production line, and preparing liquid sugar in the liquid sugar production line. The white granulated sugar is produced on the basis of the decolorized syrup produced in the liquid sugar production process, so that the production process of refined white granulated sugar is simplified; meanwhile, the molasses generated by refining the white granulated sugar can be recycled