The invention discloses an extracting and purifying method of a red-brown pigment of chestnut shells, and belongs to the technical field of plant extraction separation and purification. The extracting and purifying method comprises the steps: crushing the chestnut shells to form granular raw materials; soaking the granular raw materials in an alcohol water solution with low concentration, extracting by adopting a microwave-assisted extraction method to obtain a primary pigment extract; preparing a primary pigment solution with concentration which is close to or equal to a saturated concentration from the primary pigment extract; mixing the primary pigment solution with the alcohol water solution with the volume which is 2-4 times that of the primary pigment solution, settling, filtering, concentrating to obtain a pigment concentrated solution; mixing the pigment concentrated solution with deionized water with the volume which is 9-11 times that of the primary pigment solution, settling, filtering, and drying to obtain pigment powder. The extracting and purifying method provided by the invention solves the problem of extraction and purification of the red-brown pigment of the chestnut shells; used reagents are nontoxic and pollution-free; the application field of the pigment of the chestnut shells is widened.