A process for preparing the injection of water-soluble vitamin includes such steps as thermally dissolving glycine in the water for injection while filling inertial gas, adding 12 compounds including cysteine hydrochloride, endrate disodium, vitamin C sodium, folic acid, etc, stirring, regulating pH=5.6-6.1, adding the water for injection, stirring, aseptic filtering, pouring in containers, pre-freezing, vacuumizing, filling inertial gas, pre-freezing, heating to 30-35 deg.C, holding the temp for 6-10 hr, filling inertial gas, and sealing.