The invention is applicable to the technical field of power supplies, and provides a UPS control method, which comprises the following steps: acquiring the working state of a bypass; when the workingstate of the bypass is normal, collecting the instantaneous value of the input
voltage of the bypass in real time, and determining a first
zero crossing point and a second
zero crossing point according to the instantaneous value of the input
voltage of the bypass; at a first zero-crossing point moment, switching a direct-current conversion module into a positive half-cycle
energy supply state, andswitching an inversion module into a positive half-cycle
energy supply state; and and at a second zero-crossing point moment, switching the direct-current conversion module into a negative half-cycleenergy supply state, and switching the inversion module into a negative half-cycle
energy supply state. According to the invention, when the bypass is normal, the
zero crossing point is pre-judged according to the bypass input
voltage, and the direct-current conversion module and the inversion module are switched to the positive half-cycle energy supply state or the negative half-cycle energy supply state at the same time at the two zero crossing points of one period, so that the output phases of the UPS are consistent when the bypass and the main loop supply power, and seamless switching between the bypass mode and the inversion mode is ensured.