Disclosed is a high-energy photon reaction depth positioning method based on disperse crystal. According to the method, the reaction depth of a high-energy photon is directly determined by means of the reaction depth information in a disperse crystal mapping and decoding diagram. The method comprises the steps of (a) determining the corresponding relation between the reaction depth and the decoding position of the high-energy photon, (b) setting the reaction depth positioning grade according to reaction depth positioning requirements, (c) determining the reaction depth segmentation boundary according to the reaction depth grade, and (d) positioning the reaction depth of the high-energy photon according to the high-energy photon decoding position based on the reaction depth segmentation boundary. According to the method, by establishing the corresponding relation between the reaction depth and the decoding position and the reaction depth segmentation boundary, the reaction depth information of the high-energy photon can be worked out effectively, a complex structure additional designed for depth positioning in the traditional method is not needed, cost is reduced, and simplicity and effectiveness are realized.