The invention discloses an internal mixer for rubber mixing. The internal mixer comprises an internal mixer body. A feeding opening is formed in the outer wall of one side of the internal mixer body,and a feeding hopper and a mixing chamber are formed in the internal mixer body. The feeding hopper is located above the mixing chamber, and an upward-jacking bolt is mounted in the middle of the feeding hopper. A second motor, a screw, a second guide rod, a fixing seat, a driving gear, a driven gear and a screw sleeve are arranged, during unloading, firstly, an PLC controls a first motor to startto work, the first motor drives the driving gear to rotate through a rotary shaft, the driving gear is engaged with the driven gear and drives the screw sleeve to rotate through the driven gear, thescrew sleeve is in rotating fit with the screw when rotating, and thus the purpose of screw ascending is achieved; and when ascending, the screw drives the upward jacking bolt to move upwards throughthe second guide rod till one end of the second guide rod makes contact with the screw sleeve, in the unloading process, the upward jacking bolt is started, and on the one hand, the discharging pressure of a downward jacking bolt can be relieved.