The invention discloses a composite rope vertical tensioning and fixing device which comprises a supporting platform, a tensioning portal frame, a tensioning jack, a pull rod device, a locking device,a composite rope, and a working anchor chain and a standby anchor chain which are each composed of a plurality of chain links. The tensioning portal frame comprises two supporting columns fixed to the supporting platform and a cross beam fixed to the two supporting columns, and a through hole is formed in the middle of the cross beam; the tensioning jack is fixed to the position, corresponding tothe through hole in the cross beam, of the middle of the cross beam; one end of the pull rod device is detachably connected with the working anchor chain, and the other end of the pull rod device penetrates through the through hole in the middle of the cross beam to be connected with a safety nut; and the locking device is arranged on the supporting platform and used for locking and fixing the working anchor chain tensioned by the pull rod device, and the other end of the working anchor chain is connected with the composite rope. The device can be used for regulating the tensioning force of the composite rope conveniently and performing locking and fixing, and deflection deformation of the composite rope under the effect of stormy wave flow is effectively restrained.