Abstract: A miniaturized gravity-driven mercury-dropping pump was developed. The pump consists of a piece of 8 cm long capillary (200 μm i.d.) connected at both ends to two circular mercury reservoirs in the same construction for mercury dropping. The working: Principle of the pump was discussed with the influencing factors on its performance in conceptual design analyzed, such as the level variation of mercury, the inner diameter and length of the capillary, the loading flow resistance and the sectional area of the mercury reservoirs. Some of the figures of merit of the present mercury-dropping pump include its miniaturized dimensions, self-driven, free of mechanical parts, controllable flowrates by readily adjusting the differences between mercury levels via tilting the pump body and long-term repeated operation by overturning the pump body. A flow rate 1.09-1.34 μL/min was obtained within 4 hr successive operation, with an average flowrate 1.22 μL/min and precision 4.0% RSD (n = 24) provided. The pumping pressure was tested up to 4.5 kPa.