A system for detecting swelling of a battery comprising one or more battery modules, the system comprising: the one or more battery modules; a plurality of detecting units, a plurality of detecting units being provided in each of the one or more battery modules and each detecting unit being configured to detect gas branched from a battery cell of the corresponding battery module; a control unit configured to select the largest detection value among the detection values of the respective detecting units, determine a level of the selected detection value according to a size of the selected detection value, and control an operation of a peripheral apparatus based on the corresponding level; and a switch unit provided in a connection path of the battery pack and an external power source and configured to be turned on and off according to a signal of the control unit, wherein the control unit is configured to compare the detection value of each of the detecting units with a predetermined threshold value, select the largest detection value among the detection values exceeding the threshold values, and determine a level of the selected detection value according to the size of the selected detection value, wherein the level of the selected detection value is determined as one of a first level, a second level, and a third level according to the degree of swelling risk, wherein when the level of the selected detection value is determined as one of the first level, the second level, and the third level, the control unit is configured to transmit a vehicle speed control signal based on the corresponding level to an electronic control unit of a vehicle. the one or more battery modules; a plurality of detecting units, a plurality of detecting units being provided in each of the one or more battery modules and each detecting unit being configured to detect gas branched from a battery cell of the corresponding battery module; a control unit configured to select the largest detection value among the detection values of the respective detecting units, determine a level of the selected detection value according to a size of the selected detection value, and control an operation of a peripheral apparatus based on the corresponding level; and a switch unit provided in a connection path of the battery pack and an external power source and configured to be turned on and off according to a signal of the control unit, wherein the control unit is configured to compare the detection value of each of the detecting units with a predetermined threshold value, select the largest detection value among the detection values exceeding the threshold values, and determine a level of the selected detection value according to the size of the selected detection value, wherein the level of the selected detection value is determined as one of a first level, a second level, and a third level according to the degree of swelling risk, wherein when the level of the selected detection value is determined as one of the first level, the second level, and the third level, the control unit is configured to transmit a vehicle speed control signal based on the corresponding level to an electronic control unit of a vehicle.