The invention belongs to the field of constructional engineering, and particularly relates to a cable force compensation device applicable to a service-period curtain wall cable net. The cable force compensation device comprises an upper clamping block, a lower clamping block, fastening bolts and an isolating layer. The isolating layer winds the position of the outer surface of a fastened cable body which is fastened between the upper clamping block and the lower clamping block, and the upper clamping block and the lower clamping block are fastened through bolts. The cable force compensation device can be used for cable force compensation upon the service-period curtain wall cable net built and put into use, the scope of compensation can be fully covered rather than just being confined to the end of a cable; a cable force compensation method can be implemented without dismantling glass and cable clamps and destroying existing architectural decoration, and nondestructive construction operation can be achieved; the range of cable force comprehension can be adjusted and the numerical value of the cable force comprehension can be accurately controlled by adjusting curved angles of grooves, vector height distance the cable deviates the axis and prestress of the fastening bolts; the cable force compensation device is simple in structure, low in cost and applicable to large-scale promotion and use.