Abstract: Quantitative evaluation of blasting damage has always been a matter of great concern to the engineering blasting fieldIn this paper，an active confining pressure and boundary constraint device is designed and developed to solve the problem of boundary constraint in traditional indoor small specimen blasting and punching problem caused by poor sealing effectBased on CT scan and 3D reconstruction，the method of testing and calculating the rock damage after blasting is proposedThe method can be used to quantitatively evaluate and analyze the degree of damage and fracture after the rock specimen is blasted with small chargeUsing the device and the method，the laboratory blasting test of red sand stone of small charge under different relative confining pressure was carried out，the CT scan and CT image binarization processing of the postexplosion specimen was carried out，and the rock specimen was reconstructed based on Mimics 1001It is found that the reconstructed model has strong similarity with the real postexplosion specimenFinally，fractal dimension and damage degree are calculatedThe research results provide a new idea for blasting damage evaluation.