Necking type electromagnetic water meter

The utility model relates to the field of electromagnetic water meters, and discloses a necking electromagnetic water meter which comprises an electromagnetic water meter body and a limiting mechanism, a groove body is formed in the electromagnetic water meter body, a sealing ring is fixedly arranged in the groove body, a venturi tube is in sealing contact with the interior of the sealing ring, and the venturi tube is connected with the limiting mechanism. The limiting mechanism is arranged on the electromagnetic water meter body, the limiting mechanism is used in cooperation with the venturi tube, the limiting mechanism comprises two assembling blocks, two first positioning plates and a second positioning plate, the assembling blocks are fixedly installed on the front side of the electromagnetic water meter body, and moving holes are formed in the side faces of the assembling blocks; the first positioning plate is installed in the moving hole in a sliding mode, two first positioning grooves are formed in the