The invention relates to a liquid sampling device, and discloses a continuous micro intravenous drip instrument, which comprises a syringe and a syringe propelling mechanism. The syringe propelling mechanism comprises a barrel, a lead screw, a graduated disc and a graduated disc rotating unit, the lead screw and the graduated disc are disposed in the barrel, the graduated disc is provided with a hollow cavity, one end of the lead screw is abutted onto a push rod of the syringe, the other end of the lead screw is connected with the graduated disc rotating unit in a threaded manner, the graduated disc rotating unit rotates to drive the graduated disc to rotate, simultaneously, the lead screw moves along the axial direction of the graduated disc, and then the syringe is pushed. When the graduated disc rotates by a circle, the displacement of the lead screw moving along the axial direction of the graduated disc is 0.6mm. The lead screw is connected with the graduated disc rotating unit inthe threaded manner, and propelling quantity of the syringe can be adjusted accurately. The continuous micro intravenous drip instrument is simple in structure, can be used for standard high-precision syringes, saves cost, and further comprises a positioning ring distributed equally, so that the application range of medicine propelling quantity is large.