The invention discloses a pre-processing system and method of crushed coal pressure gasification waste water, and belongs to the field of waste water processing. The system comprises a demulsification reaction device, a first level flocculation reaction device, a first level mud and water separation device, a pipeline mixer, a fenton reaction device, a second level flocculation reaction device and a second level mud and water separation device, wherein the demulsification reaction device is connected with the first level flocculation reaction device, the first level mud and water separation device, the pipeline mixer, the fenton reaction device, the second level flocculation reaction device and the second level mud and water separation device in sequence. The demulsification reaction device is provided with a water inlet pipe used for introducing the crushed coal pressure gasification waster water; the second mud and water separation device is provided with a water outlet pipe used for discharging the processed yielding water; the demulsification reaction device is provided with a first ferrous sulfate dosing pipe; the fenton reaction device is provided with a second ferrous sulfate dosing pipe.