The invention provides a manufacturing method of a glass fiber reinforced plastic cover plate used for a power cable tunnel and belongs to the field of mechanical components. The method includes the steps that a glass fiber reinforced plastic plate is produced through a conventional glass fiber reinforced plastic production technology, and a layer of aluminum alloy cellular board is arranged between at least two layers of glass fiber reinforced plastic; the meshing size of the aluminum alloy cellular board is 20 mm in the direction of length and width, and the meshing size of the aluminum alloy cellular board is 5 mm in the direction of thickness; the thickness of the glass fiber reinforced plastic layers and the thickness of the aluminum alloy cellular board each account for 50%, glass fiber reinforced plastic is arranged on the outer layer, and the aluminum alloy cellular board is arranged on the inner layer; the load bearing strength of the cover plate used for the power cable tunnel is improved through an aluminum alloy enhancement layer, the special requirement of the cover plate used for the power cable tunnel is met through the low weight, the good insulation performance and the excellent corrosion resistance of the glass fiber reinforced plastic, and the requirements in actual work can be totally met.