The invention relates to a controllable segmental anchorage device for unbonded tendons as well as an assembly method and application thereof and belongs to the field of prestressed concrete structure application. The controllable segmental anchorage device comprises a bidirectional anchor cup, left clamping pieces, a spring, an inhaul cable and right clamping pieces, wherein a through hole is reserved in the axis of the long direction of the bidirectional anchor cup, and a vertical hole is formed in the upper part of the bidirectional anchor cup; the left (right) clamping pieces are 2-3 conical clamping pieces, an oblique perforated ear plate is arranged on the tail part of each left (right) clamping piece, and the inclined direction of the oblique perforated ear plates is opposite to the conical direction of a left conical hole; the spring is connected to the oblique perforated ear plates at the tail parts of the left clamping pieces and the right clamping pieces; the inhaul cable penetrates through the spring, and two ends of the inhaul cable penetrate through the vertical hole of the bidirectional anchor cup; through changing the working condition of the controllable segmental anchorage device, the purpose of segmenting multi-span continuous prestressed girders is realized, so that the purposes of reducing the prestress loss and avoiding the influence on the full span and the mutual influence between the spans are achieved.