The utility model discloses a connection pipe for a high-pressure water injection flow meter. The connection pipe comprises a flange, a casing pipe, a sealing ring, a pressing plate and a water injection pipe; the pressing plate is annular; the casing pipe and the pressing plate are sleeved on the water injection pipe; the sealing ring is arranged between the casing pipe and the water injection pipe; the pressing plate is tightly pressed on the sealing ring; and a flange is arranged at one end of the casing pipe, which is far away from the pressing plate. According to the connection pipe for the high-pressure water injection flow meter provided by the utility model, the casing pipe can slide on the water injection pipe, so that the sealing connection of the casing pipe and the water injection pipe can be ensured in a sliding process. The flange is pushed to a direction far away from a flow meter after a bolt for connecting the flow meter is dismounted, so that the flow meter can be easily released from the flange, and the flow meter can be dismounted without levering the flow meter.