Water electrolysis hydrogen production system and control method thereof

The invention discloses a water electrolysis hydrogen production system and a control method thereof. The water electrolysis hydrogen production system comprises a plurality of hydrogen production subsystems, each hydrogen production subsystem comprises an electrolytic bath, a gas treatment device, a gas output pipeline, a gas utilization pipeline and a gas waste pipeline, the gas treatment device is connected with the electrolytic bath, one end of the gas output pipeline is connected with a gas output port of the gas treatment device, and the other end of the gas utilization pipeline is connected with the gas waste pipeline. The other end of the gas output pipeline is simultaneously connected with a gas utilization pipeline and a gas waste pipeline, an analyzer and a flowmeter are arranged on the gas output pipeline, and a first regulating valve is arranged on the gas waste pipeline; and the gas mixing unit is connected with the gases of the plurality of hydrogen production subsystems through pipelines, and