Abstract: The oblique crack arrest of 7A04 super hardness aluminium was studied by super pulse current discharge with home-made equipment ZL-2. Under the super impulse current discharge, there is a strong detouring phenomenon at the crack tip. The metal melt around the oblique crack tip passivates the crack tip and inhibits the cracking trend of main crack source. The microstructures of the aluminium alloy before and after crack arrest were observed by metallographic microscope, and the fracture morphologies were compared macroscopically and microcosmically. Tension tests of samples with an oblique crack before and after crack arrest were done by using a PC-control universal tester. The results indicates that on the moment of crack arrest, the metal around the crack tip melts, the microstructure at the crack tip appears super refine, the work of crack expansion increases, and the tensile mechanical properties of specimens are improved.