The invention relates to a circulating heating system and method for nuclear power station hydraulic test. The circulating heating system comprises a heater, a water feeding loop and a water discharging loop; the water feeding loop is connected with the heater and used for delivering water heated by the heater into a vapor generator; the water discharging loop is connected with the heater and usedfor discharging water in the vapor generator out of the heater. The heater, the water feeding loop, the vapor generator and the water discharging loop form a closed-ring circulation, thereby achieving continuous heating to the vapor generator with sufficient use of heat, high heating efficiency and short duration as needed, particularly achieving the effect of heating a tube sheet of the vapor generator to reach temperature as needed rapidly and further improving project quality and level of safety management. Besides, after the heating efficiency is increased, the electric power of the heating system can be reduced, so that power load of the upstream can be reduced and equipment redundancy can be improved.