The present invention relates to a hemoglobin oxygen carrier based on double chemical modification and its preparation method and application. In the hemoglobin oxygen carrier based on double chemical modification, two Val‑1 (α) residues are carboxymethylated, and two Lys ‑99(α) residues are intramolecularly cross-linked. Two of the Lys-99(α) residues are intramolecularly cross-linked, and the fumarimide bridge formed can change the electrostatic interaction of adult hemoglobin (HbA) molecules, stabilize the tense state (T state) of HbA, and reduce its Oxygen affinity; Val‑1(α) is located at the αα‑end of the central cavity of HbA, and can participate in the formation of salt bridges that help stabilize the structure of the relaxed state (R state). Carboxylation modification will destroy these salt bridges and reduce HbA The stability of the R state makes the quaternary structure of HbA shift from the R state to the T state, reducing the affinity of HbA for oxygen. The invention organically combines the two modification means, improves the stability of the HbA tetramer, enhances the electrostatic interaction, improves the binding state of the oxygen binding region and oxygen, and has strong oxygen carrying / releasing activity.