The invention provides an electrostatic separation device and method for catalytic cracking oil slurry purification treatment, and belongs to the technical field of catalytic cracking oil slurry purification treatment and resource comprehensive utilization. An electrostatic separator shell in the device is connected to the ground to form an electrostatic separator cavity, and a purified oil slurrycollector and an oil slurry raw material distributor respectively divide the electrostatic separator cavity into a first chamber, a second chamber and a third chamber. First through holes and secondthrough holes are formed in the oil slurry raw material distributor and the purified oil slurry collector. High-voltage electrodes are arranged in the second chamber, insulating sleeves sleeve the high-voltage electrodes, high-voltage introduction interfaces are formed in the electrostatic separator shell, penetrate through the electrostatic separator shell and the insulating sleeves and are connected with the high-voltage electrodes, and the remaining space part in the second chamber is filled with a filler. The device has the advantages of simple structure and convenient operation, the problem that a conventional separation method cannot remove solid ultrafine particles is solved, the removal efficiency of solid particles is improved, and the electrostatic separation device is suitable for long-cycle operation. A purification treatment method is simple, and the effect is good.