The invention discloses a continuous compound forming method for a copper-aluminum composite plate. The method comprises the following steps of: preparing an aluminum billet into a plate-like structure through a device and making the plate-like structure generate plastic deformation to form an aluminum plate base material in a sealed state of the aluminum billet; sequentially rolling the aluminumplate base material and two copper plates to form a three-layer composite plate structure which is prepared by compounding the copper plates on the two surfaces of the aluminum plate base material; and finally further pressing and straightening the structure through a straightening mechanism to form a composite plate or strip. The device comprises a pair of an extrusion roller and a first rollingroller which are rotatably arranged opposite to each other and are in extrusion fit with each other, wherein a first rolling region is formed between the extrusion roller and the first rolling roller; a part on the outer circumferential surface of the extrusion roller close to an inlet of the first rolling region is provided with an aluminum material forming die; a part of the aluminum material forming die close to the inlet of the first rolling region is provided with an aluminum material deformation region; the peripheral surface of the first rolling roller is provided with a guide block corresponding to an outlet of the first rolling roller; the inner wall of the guide block opposite to the first rolling roller is matched with the peripheral surface of the first rolling roller at an equal distance to form a guide passage; a part close to the outlet of the guide passage is rotatably provided with a second rolling roller; and a second rolling region is arranged between the second rolling roller and the first rolling roller.