The utility model relates to a cydariform off circuit tap changer with all -round ring shielding cage, the apparatus comprises a support body, go up insulating support, lower insulating support, the back shaft, moving contact and static contact, the circumference equipartition is followed to a plurality of static contacts, and fixed alternate at last insulating support under and on the insulating support, the back shaft is fixed to be alternated at last insulating support insulating support's under and middle part, the outside of supporter is fixed with the ring shielding cage, the ring shielding cage includes a plurality of voltage -sharing posts of following the circumference interval arrangement and a plurality of equalizer rings of following the axial interval arrangement, the equalizer ring is crossing fixed with the voltage -sharing post, the position one -to -one of a plurality of voltage -sharing posts and a plurality of static contacts, one side that the equalizer ring at both ends is close to the moving contact all is equipped with the supporting shoe, a plurality of supporting shoes are fixed respectively in the interval of two adjacent voltage -sharing posts. The utility model discloses rationally shelter from outside electric field to the infiltration of switch body, greatly reduced not uniform electric field to switch body or the influence of switch body to neighbouring conductor.