The invention belongs to the field of computer assembly, in particular to a dust removal device after assembly of a computer main case. The technical problem to be solved by the present invention is to provide a dust removal device after assembly of the computer main case which can reduce the labor intensity, improve the dust removal efficiency and improve the quality of the case. In order to solve the above-mentioned technical problems, the present invention provides such a dust removal device after the computer main case is assembled, which includes a first bracket, a workbench, a first slide rail, a first slider, a placement frame, a support plate, and a first bearing seat , main air pipe, rotating shaft, gear, air spray head, joint, etc.; the top of the first bracket is provided with a workbench, and the top of the workbench is horizontally connected with the first slide rail by means of bolt connection. The present invention blows air to the cabinet by swinging the air spray head left and right to blow away the dust in the cabinet, so that the dust in the cabinet can be removed, the labor intensity can be reduced, and the dust removal efficiency can be improved.