Flowmeter testing device and method facilitating replacement of butt joint pipe diameter

The invention discloses a flowmeter testing device and method facilitating butt joint pipe diameter replacement, the device comprises a detection device, a detection pipe and a tail pipe, the detection pipe is connected to the position of a detection gas output end of the detection device, pipe heads are arranged at the opposite ends of the detection pipe and the tail pipe, butt joint pipes are inserted into ports of the pipe heads, and the butt joint pipes are connected with the tail pipe. By arranging the locking rod, the threaded rotating ring and the locking assembly, the butt joint pipe can be fixed or disassembled during use, during disassembly, the handle is rotated to drive the threaded rotating ring to rotate, and the threaded rotating ring rotates to push the locking rod to move in the direction away from the pipe head to unlock the locking disc; after the locking block is removed, the locking block can be retracted into the retraction cavity under the action of the electromagnet, the locking disc c