A cable magnet ring of adjustable length and able to include anti-EMI magnets of different strengths includes a bracket and a number of pairs of magnetic blocks. The bracket includes a first connecting member and a second connecting member detachably mounted to the first connecting member. The magnetic blocks are detachably received in the first and second connecting members. The first connecting member is movable relative to the second connecting member, to adjust a length of the bracket. Through holes for receiving a cable are defined in the shape of each pair of magnetic blocks, in the first connecting member, and in the second connecting member.