The invention belongs to the field of tumor treatment and the field of molecular immunology, and relates to an antibody for resisting human epidermal growth factor receptor 2 (HER2), as well as a medical composition and use of antibody, in particular to the antibody for resisting Her2 or an antigen binding fragment of the antibody for resisting Her2. The antibody for resisting Her2 comprises a first heavy chain and a second heavy chain, wherein according to the first heavy chain, a variable region of heavy chain (VH) of the first heavy chain comprises a complementarity-determining region (CDR) of which the amino acid sequence is SEQ ID No: 1-3, and the amino acid sequence of the CH of the first heavy chain is as shown in SEQ ID No: 7; according to the second heavy chain, a variable region of heavy chain (VH) of the second heavy chain comprises a complementarity-determining region (CDR) of which the amino acid sequence is SEQ ID No: 4-6, and the amino acid sequence of the CH of the first heavy chain is as shown in SEQ ID No: 8. Compared with the combination of two antibodies of trastuzumab and pertuzumab, the antibody disclosed by the invention has higher cell direct killing activity and higher antibody dependent cellmediated cytotoxicity (ADCC) activity; the complement-dependentcytotoxicity (CDC) activity of the two antibodies of trastuzumab and pertuzumab is equivalent to that of the antibody disclosed by the invention; the antibody disclosed by the invention adopts a structure of a normal antibody; and fucose is also knocked out, so that the ADCC activity is improved.