A system for producing hydrogen with electric power of a thermal power plant through electrolytic tanks comprises a power network peak regulation control system, a power transmission and distribution and power supply system, a water electrolysis hydrogen production system, a hydrogen collection, purification and outward-conveying system, a cooling water waste heat recovery system, an electrolytic tank high-temperature steam supply system and a purified water preparation and water replenishing system. According to the power transmission and distribution and power supply system, an interval is newly added on a power plant out-line bus and is provided with an electric switch. The electric switch is connected with a step-down transformer and an inverter through a power transmission power network. The other ends of the step-down transformer and the inverter are connected with the water electrolysis hydrogen production system. The water electrolysis hydrogen production system comprises at least one in an alkaline aqueous solution electrolysis hydrogen production device, a solid polymer electrolysis hydrogen production device and a high-temperature solid oxide electrolysis hydrogen production device. The alkaline electrolytic tank is cooled by condensed water, thus efficiency is improved, power plant main steam serves as a steam source of the high-temperature solid electrolytic tank, peak regulation electric quantity of the power plant is fully used, and valuable peak regulation loads are provided for clean energy network supply.