Abstract: The space between blast-holes is the main factor influencing on the desensitization of industrial explosives. The relation of pressure desensitization to the space between explosive charges was analyzed and ideally modeled. Two concepts of critical dead-pressing space and critical desensitization space were introduced and discussed based on the practice and it is reasonable to depict the relation by the two concepts. It is shown that the two concepts are helpful for understanding the desensitization of explosives and guidable to design blasting holes in millisecond blasting.