Hydraulic oil in the hydraulic system of large hydraulic press must be guaranteed to have certain cleanness and temperature. As the power source of filtering cooling and heating system, screw pump plays a very important role in the whole system. The composition and operation principle of filtering cooling and heating system for 75 MN aluminum extruder were introduced. The screw pump type was confirmed based on the requirements of rotate speed, structure and flow. Finally the precautions of screw pump in using were summarized.  The practice results show that the selected screw pump is suitable and the system operates well for three years.