An embodiment of the invention discloses a processing method of a PCB stepped groove. The method comprises the following steps of daughter board layer slotting: slotting is performed on corresponding positions of parts of the daughter board layers which form the PCB and the slotting is also performed on corresponding prepreg layers; matching board filling: all the daughter board layers and the prepreg layers which form the PCB are laminated successively, the daughter board layers which are provided with grooves and grooves on the prepreg layers are successively aligned layer-by-layer so as to form a semi-finished-product stepped groove and then gaskets of a non-silica-gel-class high temperature resistance and high pressure resistance material are filled in the semi-finished-product stepped groove; laminating: through flow filling and bonding of a prepreg, the daughter board layers form a multilayer PCB; gasket removing: the gaskets in the PCB after a laminating step are directly removed so as to obtain a finished-product stepped groove. By using the processing method of the PCB stepped groove, size precision of the PCB stepped groove is guaranteed; a quality of the PCB stepped groove is increased and there is no defective gum on a bottom of the groove; delamination of the prepregs surrounding the stepped groove can be prevented, and deformation and collapse of the PCB can be prevented too; cost is saved.