A control program structure and its method are disclosed which is capable of controlling a hardware source of an ATM switching system from an external source through a standard interface. The control program structure of an ATM switching system including: a GSMP master function unit mounted on a processor board existing at an external source of an ATM switching system, for performing a master function of a GSMP (general switch management protocol); a protocol processing function unit mounted on a processor board inside a switching system, for processing a slave function of a GSMP; and a plurality of resource control function units each mounted on processor boards distributed in the switching system, for controlling a hardware resource of the system according to a request message of the protocol processing function unit.