The invention discloses an automatic assembly process and device for a motor shell, and relates to the field of motor assembly. The method comprises the steps of providing a workpiece, wherein the workpiece comprises a barrel shell, a bearing and a magnetic body, and an inner cavity is formed in the barrel shell; assembling a bearing, conveying the barrel shell to an axial pressing mechanism, pressing the bearing into the barrel shell, and enabling the bearing to be fixed in a bearing groove; assembling the magnetic body, conveying the barrel shell in which the bearing is pressed to a magneticbody installing mechanism, and installing the magnetic body in the inner cavity; conducting a dust removal process for performing dust removal treatment; conducting a magnetizing step for magnetizingthe magnetic body; and conducting post-processing for detecting and processing the magnetized shell assembly. According to the invention, the process is simple, the cylinder shell, the bearing and the magnetic body can be rapidly and accurately installed in the barrel shell, the working efficiency is improved, rapid assembling of the motor shell is achieved through the axial pressing mechanism, the magnetic body installing mechanism, a dust collection mechanism, the magnetizing mechanism and other mechanisms, the device space occupation ratio is small, accurate and efficient assembling of themotor shell is achieved, the labor cost is reduced, and the working space is saved.