Abstract: In order to avoid the problem that the characteristic points of the reflected signal are difficult to identify in the process of bolt nondestructive testing, the box dimension in the fractal dimension is introduced into the analysis of the reflected signal of the bolt nondestructive testing.In order to study the relationship between the ultimate bearing capacity of the anchor bolt and the box dimension, the research is carried out from two angles of anchoring defect degree and anchoring agent properties by setting the defect section filled with dry sand and making anchoring agents with different proportions.The reflection signal of the anchor rod is collected on the ground under the Gujiao Dongqu mine, and the drawing test is carried out after the analysis is completed.The results show that the more the number of defects in the bolt, the smaller the ultimate bearing capacity and the higher the response curve box dimension; the properties of anchoring agents change with the increase in sand content, the ultimate bearing capacity first increases and then decreases, the response curve box dimension increase.In the same roadway in the mining area, the larger the box dimension of the response curve is, the greater the working load is, and the ultimate bearing capacity of anchoring tends to decrease.