The invention provides a fracturing backflow fluid electroflocculation pretreatment device and method. The device comprises a box body, an electroflocculation device, a liquid feeding pump, a power supply cabinet and a control cabinet, wherein the electroflocculation device, the feeding pump, the power supply cabinet and the control cabinet are arranged in the box body; a liquid inlet of the electroflocculation device is connected with the liquid inlet pump through a liquid inlet pipe; a liquid outlet of the electroflocculation device is connected with a liquid outlet formed in the bottom of the box body through a liquid outlet pipe; the electroflocculation device and the liquid feeding pump are respectively and electrically connected with a power supply arranged in the power supply cabinet; the electroflocculation device is also electrically connected with a controller arranged in the control cabinet; the controller is electrically connected with a touch screen. The device also comprises a slag scraping pool arranged outside the box body, a chemical adding sedimentation pool and a plate frame press filter; the slag scraping pool, the chemical adding sedimentation pool and the plate frame press filter are sequentially connected in series; an inlet of the slag scraping pool communicates with the liquid outlet through a pipeline. Through the work procedures of filtering, electroflocculation multivalent metal ion removal, press filtering and the like, the suspension contents, the turbidity and the chromaticity of the water quality are reduced to the greatest degree; the consumption of chemicals is low, so that the outlet water of the backflow fluid can reach the technical standard requirements of re-prepared fracturing fluid.