Computer mainframe box convenient for mounting mainboard

The invention discloses a computer mainframe box convenient to install a mainboard, and relates to the technical field of computer mainframe boxes, the computer mainframe box comprises a mainframe box shell, a rectangular frame is fixedly arranged on the inner wall of one side of the mainframe box shell, and rotating shafts rotationally connected with the rectangular frame are distributed on the inner wall of the rectangular frame at equal intervals; blade plates matched with the inner wall of the rectangular frame are distributed on the inner wall of the rectangular frame at equal intervals and fixedly arranged on the outer wall of a rotating shaft in a sleeving mode, one end, penetrating through the outer wall of one side of the rectangular frame, of the rotating shaft is fixedly connected with a gear, and an L-shaped plate is fixedly arranged at the top end of the rectangular frame; according to the computer case, the leaf plates in the rectangular frame are automatically rotated to be opened and closed in