Precise urine volume meter

The invention discloses a precise urine volume meter. The precise urine volume meter comprises a metering cylinder provided with containing marks, an outlet connecting pipe, an anti-counter flow inner plug, and an inlet connecting pipe; one end of the outlet connecting pipe is connected with an outlet of the metering cylinder, the other end of the outlet connecting pipe is used for being connected with a drainage bag; an outlet switch is arranged on the outlet connecting pipe; the anti-counter flow inner plug is fixedly sleeved with an inlet of the metering cylinder, the upper part of the anti-counter flow inner plug is matched with the inner wall of the inlet of the metering cylinder in a sealing manner, a gap is left between the lower part of the anti-counter flow inner plug and the inner wall of the inlet of the metering cylinder, an inner hole is formed in the anti-counter flow inner plug, the upper end of the inner hole is opened, a plurality of side holes communicated with the inner hole are formed in t