The traditional one-stage mixing method is limited to the preparation of softer or slower vulcanizates and the use of small and medium-sized equipment. This is determined by the cooling requirements of the mixer equipment after masterbatch preparation. It is composed of two channeling internal mixer units. The former equipment is above the latter equipment. The upper mixer can be sheared to produce a section of master batch. The mixer can keep high speed, high temperature or long time mixing for better uniform dispersion. As soon as the normal mixing cycle of the mixer is completed, the hot rubber is discharged into the mixer below. The volume of the lower mixer is larger than that of the upper mixer, with a lower speed and strong cooling capacity, which can quickly reduce the rubber temperature from 140 degrees to below 100 degrees in less than 2 minutes, and then reduce the reactive compounding agent. Add to the internal mixer below, mix for 1 to 2 minutes at a typical rotor speed of 15 rpm and discharge.