Closed device capable of accurately measuring drainage liquid

The utility model provides a closed device capable of accurately measuring drainage liquid. Relating to the field of drainage liquid measurement, the device comprises a large-capacity main measuring cup, a small-capacity auxiliary measuring cup, a straight cylinder, a piston and an adjusting screw rod, scales are arranged on the main measuring cup and the auxiliary measuring cup; the top of the main measuring cup is in threaded connection with a cover; the auxiliary measuring cup is in a closed shape; the auxiliary measuring cup is communicated with the main measuring cup through a hose; the straight barrel is vertically arranged at the top of the auxiliary measuring cup, the bottom of the straight barrel is communicated with the auxiliary measuring cup, the piston is vertically matched inthe straight barrel in a sliding mode, the bottom end of the adjusting screw is pivoted to the piston, the top end of the adjusting screw extends out of the top of the straight barrel and is in threaded connection with the s