The invention discloses a purification preparation method of a guar gum and derivatives of guar gum. The purification preparation method of the guar gum and the derivatives of guar gum is characterized in that a sprinkling washing and continuous belt vacuum dewatering combined device is used for preparing high-purity guar gum and the derivatives of guar gum. The purification preparation method of the guar gum and the derivatives of the guar gum has the advantages that the conventional centrifugal washing intermittent purification process of the guar gum derivatives is changed, the belt vacuum filter device is adopted, the automation degree and the production process of the washing purification process can be improved by use of a washing dewatering method combining sprinkling washing and belt vacuum filtration, and meanwhile, the amount of water needed by washing and wastewater generated by washing are reduced, and therefore, the wastewater disposal amount is reduced
