The invention discloses a cohesive soil large-scale triaxial sample consolidating apparatus and a consolidating method thereof. The consolidating apparatus comprises a triaxial sample, a pedestal, a top cover, a rubber gasket, an electrode, a DC power supply, a bottom water penetrating board, a top water penetrating board and a combined insulated board; periphery of the cohesive soil triaxial sample is isometrically provided with electrodes, a central axis of the triaxial sample is provided with electrodes, electrodes arranged at the periphery are connected with the bottom water penetrating board at the bottom of the triaxial sample, the bottom water penetrating board is communicated with a DC power supply '-'by the combined insulated board, the electrode arranged on the central axis is connected with the top water penetrating board, the top water penetrating board is communicated with the DC power supply '+' by the combined insulated board, and the combined insulated board is composed of an insulated board, a spring and a contact. When the apparatus is used, the triaxial sample is prepared on the pedestal, simultaneously electrodes are arranged in the triaxial sample, communication between electrodes and leads are guaranteed, a rubber membrane is bundled, a confining pressure is applied, and the DC power supply is powered on for carrying out the triaxial sample consolidation. The consolidating apparatus has the advantages of simple structure, convenient operation, reliability, safety, substantially shortened consolidating time, and reduced test time and manpower.