The invention relates to a pressure reducer air supply loop adopting redundant design and a control method. The pressure reducer air supply loop comprises pressure reducers, electromagnetic valves, hand stop valves, pressure gauges and a pressure sensor which are arranged on a low-temperature propellant pressurization air source intake pipeline. A first throttling valve, a second throttling valve, a third throttling valve and a fourth throttling valve adjust the pressure reducers. The pressure gauges monitor pressure of outlets of the pressure reducers. The pressure sensor monitors air supply pressure. Switching of the pressure reducers is controlled by the three-position two-way electromagnetic valves. According to the pressure reducer air supply loop adopting redundant design and the control method, redundancy of the pressure reducers is achieved, the pressure reducers can be electrically switched according to collected data, the requirement for a narrow window of air supply in a task is sufficiently met, the single-point problem of ground pressurization air supply of a low-temperature propellant rocket is solved, the goal of zero-window launching is realized, and rocket launching reliability is improved.