The invention discloses a machining process of a large hydraulic plate shear rack, and belongs to the field of plate shear machining. The machining process of the large hydraulic plate shear rack comprises the machining steps that 1, wallboards and a front face plate are machined; 2, a bracket is welded, and a reference surface is machined; 3, the wallboards and the front face plate are welded; 4, a top supporting beam is welded between the two wallboards; 5, the bracket is intermittently welded and fixed; 6, cooling is carried out after fire spraying heating, and deformation is eliminated; 7, the bracket is welded again; 8, overall machining is carried out. By means of the machining process of welding method control, fire spraying deformation correction and overall machining, the deformation quantity of the rack during welding machining is reduced, size precision is improved, the product machining quality of a plate shear can be improved, and the service life of the plate shear can be prolonged.