Provided is a modified double-stranded oligonucleotide, in which the sense strand comprises a nucleotide sequence 1, the anti-sense strand comprises a nucleotide sequence 2, the nucleotide sequences 1 and 2 are both 19 nucleotides in length, and in the direction from 5′ end to 3′ end, nucleotides at positions 7, 8 and 9 of the nucleotide sequence 1 and nucleotides at positions 2, 6, 14 and 16 of the nucleotide sequence 2 are all fluoro-modified nucleotides, and each nucleotide at other positions is independently one of non-fluoro-modified nucleotides. Further provided are a pharmaceutical composition and a conjugate comprising the oligonucleotide, and pharmaceutical use thereof.