A portable type of automatic measuring apparatus for measuring orifice plate. It includes foundation supporter, orifice plate fixed structure and measuring mechanism. The characteristic of orifice plate fixed structure is that rotary table and computer interface is installed on the foundation support. The rotary table has a table-board and bottom base. A moving guide mechanism in Y direction matched each other is installed between the toundation support and bottom base of the rotary table. Portal frame type slide guide of the foundation support is located on the upper part of the rotary table. Said measuring mechanism includes measuring microscope, displacement sensor of optical grating in X and Z directions that are located above the rotary table. The bottom bases of sensor in X and Z directions as well as the bottom base of the measuring microscope are set up on portal frame type slide guide of the foundation support. The output ends of said sensors in X and Z directios are connected to the ports of computer.