Telomere is an emerging target for the treatment of human cancers. Here, we report a structure-based approach to sequence-specific cleaving of human telomeric DNA by G-quadruplex formation. Oligonucleotide with multiphosphonate [DNA-EDTP-Ce(IV)] at the 5' end binds to human telomere DNA by G-quadruplex formation and causes a sequence-specific strand break. These results provide the first proof of concept for targeting the human telomere DNA based on G-quadruplex formation, and this may serve as a starting point for the design of more efficient telomere sequence-specific cleaving reagents by G-quadruplex formation.