The invention discloses a mounting tool for rubber bands in geotechnical triaxial test. The mounting tool comprises a shrinking platform bracket, a rubber band shrinking platform, a control handle anda rotating shaft, wherein the rubber band shrinking platform is a ring structure, and a plurality of push rods are uniformly distributed on the upper top surface of the rubber band shrinking platformalong the circumferential direction; the shrinking platform bracket is an annular cover structure and covers on the rubber band shrinking platform; the shrinking platform bracket and the rubber bandshrinking platform are provided with openings at same vertical positions; the upper top surface of the rubber band shrinking platform is connected with the inner top surface of the shrinking platformbracket through a spring; a plurality of open slots matched with the push rods are formed in the upper top surface of the shrinking platform bracket; and a clamping slot is formed in the outer wall ofthe rubber band shrinking platform along the circumferential direction. According to the mounting tool, the direct contact between human and soil samples is avoided by using the tool, and the mounting of rubber bands can be synchronously and quickly completed through the tool, thereby reducing the artificial disturbance of the soil samples and making the test data closer to the real results.