A method for preparing a bacterial polysaccharide-modified recombinant fusion protein, comprising co-expressing a recombinant fusion protein and Neisseria meningitidis O-oligosaccharyltransferase PgIL in a O-antigen ligase gene-defective bacterium, and linking a polysaccharide endogenous or exogenous for the bacterium to the recombinant fusion protein by the Neisseria meningitidis O-oligosaccharyltransferase PgIL, to obtain the bacterial polysaccharide-modified recombinant fusion protein; wherein, the recombinant fusion protein comprises an N-terminal signal peptide, a peptide fragment having a glycosylation site of Neisseria meningitidis O-oligosaccharyltransferase PgIL which is the serine at position 63 starting from N-terminus of Neisseria meningitidis pilin PilE, and a carrier protein; the carrier protein is a nontoxic mutant of Pseudomonas aeruginosa exotoxin A or a fragment of a bacterial toxin protein, wherein the fragment of a bacterial toxin protein is cholera toxin B subunit or fragment C of tetanus toxin; and the peptide fragment having a glycosylation site of Neisseria meningitidis O-oligosaccharyltransferase PgIL is a peptide fragment comprising at least the amino acids from positions 55 to 66 starting from N-terminus of Neisseria meningitidis pilin PilE and is any one of the following peptide fragments: the peptide fragment set forth in the amino acid sequence from positions 128 to 156 starting from N-terminus of SEQ ID No.32; the peptide fragment set forth in the amino acid sequence from positions 128 to 154 starting from N-terminus of SEQ ID No.34; the peptide fragment set forth in the amino acid sequence from positions 128 to 152 starting from N-terminus of SEQ ID No.36; the peptide fragment set forth in the amino acid sequence from positions 128 to 150 starting from N-terminus of SEQ ID No.38; the peptide fragment set forth in the amino acid sequence from positions 22 to 40 starting from N-terminus of SEQ ID No.48; the peptide fragment set forth in the amino acid sequence from positions 22 to 36 starting from N-terminus of SEQ ID No.50. wherein, the recombinant fusion protein comprises an N-terminal signal peptide, a peptide fragment having a glycosylation site of Neisseria meningitidis O-oligosaccharyltransferase PgIL which is the serine at position 63 starting from N-terminus of Neisseria meningitidis pilin PilE, and a carrier protein; the carrier protein is a nontoxic mutant of Pseudomonas aeruginosa exotoxin A or a fragment of a bacterial toxin protein, wherein the fragment of a bacterial toxin protein is cholera toxin B subunit or fragment C of tetanus toxin; and the peptide fragment having a glycosylation site of Neisseria meningitidis O-oligosaccharyltransferase PgIL is a peptide fragment comprising at least the amino acids from positions 55 to 66 starting from N-terminus of Neisseria meningitidis pilin PilE and is any one of the following peptide fragments: the peptide fragment set forth in the amino acid sequence from positions 128 to 156 starting from N-terminus of SEQ ID No.32; the peptide fragment set forth in the amino acid sequence from positions 128 to 154 starting from N-terminus of SEQ ID No.34; the peptide fragment set forth in the amino acid sequence from positions 128 to 152 starting from N-terminus of SEQ ID No.36; the peptide fragment set forth in the amino acid sequence from positions 128 to 150 starting from N-terminus of SEQ ID No.38; the peptide fragment set forth in the amino acid sequence from positions 22 to 40 starting from N-terminus of SEQ ID No.48; the peptide fragment set forth in the amino acid sequence from positions 22 to 36 starting from N-terminus of SEQ ID No.50. the peptide fragment set forth in the amino acid sequence from positions 128 to 156 starting from N-terminus of SEQ ID No.32; the peptide fragment set forth in the amino acid sequence from positions 128 to 154 starting from N-terminus of SEQ ID No.34; the peptide fragment set forth in the amino acid sequence from positions 128 to 152 starting from N-terminus of SEQ ID No.36; the peptide fragment set forth in the amino acid sequence from positions 128 to 150 starting from N-terminus of SEQ ID No.38; the peptide fragment set forth in the amino acid sequence from positions 22 to 40 starting from N-terminus of SEQ ID No.48; the peptide fragment set forth in the amino acid sequence from positions 22 to 36 starting from N-terminus of SEQ ID No.50.