Abstract: Through large amount of engineering practice and simulative experiments, the blast effect characteristics and differences under various topographic boundary conditions have been brought to light on the whole. Some relevent calculating formulas and criteria have been put forward. It has been fully proved that the "level boundary blast system", which is widely used both at home and abroad now, is by no means comprehen-sive but only a special case of a=0° in the multiboundary condition blast system.