The emergency boric acid injection pump for the Million-kilowatt level Nuclear Power Plant adopts a horizontal three-cylinder, single-acting, electric reciprocating plunger pump design. It is intended for rapidly injecting boric acid solution into the reactor coolant system during accident conditions to ensure core boration and maintain a subcritical state. During the initial operation of the equipment, frequent issues arose, including plunger coating corrosion, packing seal wear, and bushing rupture, which resulted in reduced sealing between the plunger and packing seal, increased return flow from the outlet side to the inlet side, and ultimately decreased pump outlet flow and pressure, severely impacting the stable operation of the equipment. This paper conducted a detailed failure analysis, including chemical composition analysis, microstructural analysis, and hardness testing, to pinpoint the root causes of the defects in the plunger, packing seal, and bushing. The analysis indicated that the bushing design lacked sufficient strength to effectively support the plunger’s weight and operational impacts. Additionally, the plunger surface coating exhibited poor stability in a concentrated boric acid environment, prone to pitting corrosion. By improving the material design of the bushing and packing seal, optimizing the material and processing techniques of the plunger surface coating, and other measures, the paper successfully addressed the issues of corrosion susceptibility in the plunger coating and wear in the packing seal and bushing in the original design. The technical indicators of the improved components were significantly enhanced, fully meeting the operational requirements at the site and improving the operational reliability of the emergency boric acid injection pump.