The invention discloses a fixing device for fractures of anterior and posterior columns of acetabulum and a use method for the fixing device. The fixing device comprises an arcus marginalis steel plate, a pubis steel plate and a posterior column side wall, wherein the integral shape is matched with anatomical structures of the inner sides of the anterior and posterior columns of acetabulum; the arcus marginalis steel plate is matched with the structure of arcus marginalis, and extends toward fossa iliaca to form the posterior column side wall; the pubis steel plate is matched with the anatomical structure of the inner side of superior pubic ramus; a pubis side wall extends toward the upper surface of the superior pubic ramus at a position near pubic tubercle; a plurality of screw holes are formed in the arcus marginalis steel plate and the pubis steel plate; the arcus marginalis steel plate and the pubis steel plate are fixed at the acetabular dissection positions by planting screws. According to the fixing device and the method disclosed by the invention, the fractures of the upper parts of the anterior and posterior columns and a quadrilateral area of acetabulum can be stably fixed, so the quality of fracture reduction and internal fixation is improved.