Abstract: During nuclear power plant operation,the coolant in the primary loop will decompose to hydrogen and oxygen under radiation condition.Oxygen will aggravate the corrosion of stainless steel in the primary loop,reducing the equipment reliability and increasing the radioactive activation products.Normally nuclear power plants use the primary loop hydrogen injection to inhibit the radiation decomposition of the primary coolant.Traditional nuclear power plant uses the chemical and volume control tank to reduce the pressure of coolant and inject low pressure hydrogen.AP1000 use the high-pressure hydrogen injection technology,because there is no chemical and volume control tank in AP1000 nuclear power plant.This paper introduces the current high-pressure hydrogen injection scheme used by AP1000,analyzes the possible problems during operation,and suggests the improved scheme.