The spatial morphology of blasting crack is the theoretical basis for a blasting design.The blasting hole of underground ultra-deep hole blasting is under the action of confining pressure,and there is no blasting free surface.Under such condition,the spatical morphology of blasting crack needs to be further studied.In order to study the influence of confining pressure on the spatial morphology of blasting crack,large scale 4000 kN true triaxial loading equipment and permitted detonating cord of coal mine are used to provide confining static load and explosive dynamic load respectively.For this study,a 300 mm×300 mm×300 mm size cement mortar cube test block is used,the equivalent explosive content is 3 g,the first,and the second and the third principal stress of the test block under confining pressure is 8.50 MPa,7.00 MPa and 5.75 MPa,respectively.The spatical morphology difference of blasting crack with and without confining pressure is compared and analyzed.It is found that the spatial morphology of the blasting crack under confining pressure is very different from that under a blasting free surface condition.Under the condition of surrounding blasting free surface,the test block was broken into fragments by blasting.The mass proportion within the range of the fragmentary size L<100 mm and 100 mm≤L<200 mm accounts for 30% and 70% of the total mass of the test block respectively,among which the mass of the large size 150 mm≤L<200 mm accounts for 55.32%.However,the quantity was small and they were all generated on the surface of the test block.Under confining pressure,a symmetrical macroscopic fracture surface which is on the hole sealing device is formed perpendicular to the direction of the second principal stress.Meanwhile,more cracks appear on other surfaces of the test block.After the test block is cut,microcracks appear on the hole wall,and obvious cracks appear on the hole wall in the pre-perforated direction.