The present invention relates to a variable disconnection apparatus which variably controls the disconnection or connection of a switch in each battery unit of a large-sized battery system according to a dangerous level of a sensed external state so as to switch to a low capacity state and a low voltage state, and a variable disconnection control method thereof. The variable disconnection apparatus of the present invention which variably controls the physical connection of a battery set unit includes: a switch which is provided at a connective line of the battery set unit so as to electrically connect or disconnect the line; a switch control module which applies an on-signal or an off-signal to the switch; and a disconnection control module which controls the switch control module according to the sensed danger level so as to change locations, numbers, and disconnection intervals of opening/shutting switches. The present invention senses when the large-sized battery system is in a dangerous state and variably controls the physical connection of the battery unit for stabilization thereof into a low capacity and low voltage state.