A working method of a modular uninterruptible power supply, UPS, wherein the method comprises: a) obtaining (31, 41) working parameters of the modular UPS, wherein the working parameters comprise an input voltage parameter, a load parameter, and a battery parameter; b) determining whether the input voltage parameter meets a preset threshold, wherein the input voltage parameter comprises a voltage amplitude and a voltage frequency; c) when it is determined that at least one of the voltage amplitude or the voltage frequency does not meet the preset threshold, adjusting working modes of S power modules of K power modules in the modular UPS to a battery power supply mode, the battery power supply mode being a working mode in which the UPS supplies an alternating current to a load based on battery power input to the UPS by a battery, so that output of the modular UPS satisfies a power requirement of a load, wherein K is a total quantity of the power modules in the modular UPS, and 1 ≤ S < K; d) determining (44, 45) a remaining power module other than a power module that provides power for the load exists in the modular UPS; and executing the following step: e) determining whether the battery parameter is less than a first threshold, wherein the battery parameter comprises a remaining battery capacity; and when the remaining battery capacity is less than the first threshold, adjusting a working mode of at least one power module of the remaining power module to a charging mode, the charging mode being a working mode in which direct current based on a mains input and direct current based on an alternating current from the load is used for charging a battery; or f) determining whether the load parameter is less than a second threshold, wherein the load parameter comprises a load capacity; and when the load capacity is less than the second threshold, adjusting a working mode of at least one power module of the remaining power module to a feedback mode, the feedback mode being a working mode in which alternating current based on alternating current from the load is fed back to a power grid; or g) determining whether an output load type indicated by the load parameter is an energy feedback load such as a motor, wherein the load parameter comprises the output load type; and when the output load type is the energy feedback load, adjusting a working mode of at least one power module of the remaining power module to a feedback mode or a charging mode. a) obtaining (31, 41) working parameters of the modular UPS, wherein the working parameters comprise an input voltage parameter, a load parameter, and a battery parameter; b) determining whether the input voltage parameter meets a preset threshold, wherein the input voltage parameter comprises a voltage amplitude and a voltage frequency; c) when it is determined that at least one of the voltage amplitude or the voltage frequency does not meet the preset threshold, adjusting working modes of S power modules of K power modules in the modular UPS to a battery power supply mode, the battery power supply mode being a working mode in which the UPS supplies an alternating current to a load based on battery power input to the UPS by a battery, so that output of the modular UPS satisfies a power requirement of a load, wherein K is a total quantity of the power modules in the modular UPS, and 1 ≤ S < K; d) determining (44, 45) a remaining power module other than a power module that provides power for the load exists in the modular UPS; and e) determining whether the battery parameter is less than a first threshold, wherein the battery parameter comprises a remaining battery capacity; and when the remaining battery capacity is less than the first threshold, adjusting a working mode of at least one power module of the remaining power module to a charging mode, the charging mode being a working mode in which direct current based on a mains input and direct current based on an alternating current from the load is used for charging a battery; or f) determining whether the load parameter is less than a second threshold, wherein the load parameter comprises a load capacity; and when the load capacity is less than the second threshold, adjusting a working mode of at least one power module of the remaining power module to a feedback mode, the feedback mode being a working mode in which alternating current based on alternating current from the load is fed back to a power grid; or g) determining whether an output load type indicated by the load parameter is an energy feedback load such as a motor, wherein the load parameter comprises the output load type; and when the output load type is the energy feedback load, adjusting a working mode of at least one power module of the remaining power module to a feedback mode or a charging mode.