The invention discloses a fully-insulated combined type photovoltaic combiner box comprising a box body a and a box body b, wherein the box body a and the box body b are rectangular box structures with an opening on one side, a door plate is arranged on the opening side of the box body a and the box body b, movably connected sealing plates are arranged on the box body a and the box body b, installing plates are installed in the box body a and the box body b, sliding blocks are arranged on the upper and lower side arms of the installing plates, and insulating films are attached to the external surfaces of the box body a, the box body b, the sealing plates and door plates. The fully-insulated combined type photovoltaic combiner box employs insulating materials to prevent rusting, reduce the frequency of regular maintenance, and reduces maintenance cost. The use period is long. A combination structure of box body a and a box body b is used, the box bodies can be expanded according to the different numbers of installation lines, and the installation is flexible.