A suspension for injection, comprising a nanocarbon-iron composite system being a composite structure which is formed by acid-treated nanocarbon serving as a carrier, and the nanocarbon contains a certain amount of carboxyl on the surface, and ferrous ions and/or ferric ions in an iron salt, wherein the carboxyl has a content range of 0.03 mmol/g-0.08 mmol/g, wherein the composite system has a particle size of 90-300 nm,
- wherein the nanocarbon-iron composite system is dispersed uniformly and stably in a mixed solution containing polyvinylpyrrolidone K30 and sodium citrate;
- in the composite system, the ferrous irons or/and ferric ions have a concentration of 1.36-13.6 mg/mL.