The invention discloses an optical system integrated design method of a box-type file shooting instrument, which comprises the following steps: firstly, a box body is prepared, a backlight illuminating system is arranged in the box body to a provide diffusing surface light source for the shooting modules of the box-type file shooting instrument, so that light with enough brightness can be provided to a file to be shot, the illuminating effect with uniform brightness can be formed on the surface of the file to be shot, and the shooting effect is improved; secondly, two transparent panels are prepared, and are overlapped or spliced on the top part of the box body in a certain included angle; thirdly, two shooting modules are arranged at the lower surface of the diffusing surface light source, a position on the diffusing surface light resource, corresponding to the vision field angle of the shooting modules, are hollowed-out, the two shooting modules are respectively corresponding to one of the transparent plates, and the light axes of the shooting modules are vertical to the corresponding transparent panels; and fourthly, the light illuminating surface of the diffusing surface light source is an upper surface, the light illuminating surface faces to the transparent plates to illuminate the file to be shot, and the file to be shot is placed on the transparent panels. The invention also discloses an optical system integrated design.