A mainboard of a terminal product, comprising a core chip of a baseband or radio frequency module, wherein: the mainboard of the terminal product is a four-layer printed circuit board comprising surface layers (10, 40) and two inner layers (20, 30) between the surface layers; the surface layers (10, 40) comprises a top layer and a bottom layer which are respectively a primary reference ground layer consisted of a ground copper sheet with a large area, and the ground copper sheets with a large area of the top layer and the bottom layer are interconnected through through vias; and the inner layers (20, 30) are primary wiring layers where wiring areas are divided by functions; characterized in that: a distance between the inner layers (20, 30) is at least twice the distance between each of the surface layers (10, 40) and the inner layers (20, 30) adjacent to the surface layer; and the wiring area at each of the inner layers (20, 30) corresponds to the ground copper sheet area with a large area at a layer adjacent to the inner layer (20, 30) or vertically arranged traveling lines at the layer adjacent to the inner layer (20, 30); wherein the ground copper sheet with a large area is an area in a reference layer that is a projection area in the reference layer of a wiring layer in a related layer and is a region with a complete ground copper sheet. the mainboard of the terminal product is a four-layer printed circuit board comprising surface layers (10, 40) and two inner layers (20, 30) between the surface layers; the surface layers (10, 40) comprises a top layer and a bottom layer which are respectively a primary reference ground layer consisted of a ground copper sheet with a large area, and the ground copper sheets with a large area of the top layer and the bottom layer are interconnected through through vias; and the inner layers (20, 30) are primary wiring layers where wiring areas are divided by functions; characterized in that: a distance between the inner layers (20, 30) is at least twice the distance between each of the surface layers (10, 40) and the inner layers (20, 30) adjacent to the surface layer; and the wiring area at each of the inner layers (20, 30) corresponds to the ground copper sheet area with a large area at a layer adjacent to the inner layer (20, 30) or vertically arranged traveling lines at the layer adjacent to the inner layer (20, 30); wherein the ground copper sheet with a large area is an area in a reference layer that is a projection area in the reference layer of a wiring layer in a related layer and is a region with a complete ground copper sheet. a distance between the inner layers (20, 30) is at least twice the distance between each of the surface layers (10, 40) and the inner layers (20, 30) adjacent to the surface layer; and the wiring area at each of the inner layers (20, 30) corresponds to the ground copper sheet area with a large area at a layer adjacent to the inner layer (20, 30) or vertically arranged traveling lines at the layer adjacent to the inner layer (20, 30); wherein the ground copper sheet with a large area is an area in a reference layer that is a projection area in the reference layer of a wiring layer in a related layer and is a region with a complete ground copper sheet.