Abstract: The Coulter Principle is an electrical method that measures the size and number of particles by using pulse signals formed by the particles as they pass through the electrically sensitive regions. At present, the Coulter counter mainly uses two methods to make the detection electrode, one is the insertion method, and the other is to integrate the microelectrode inside the micro flow channel by using the micro-nano processing（MEMS） patterning process. The insertion method often uses an electrochemically stable metal such as platinum wire to insert into the chip as a detection electrode, which has the disadvantages of introduction of air bubbles, and low detection sensitivity; micro-nano processing integrated electrode method is complicated in process and high in cost, and difficult to integrate electrodes with the flow channel. This paper introduces a new microfluidic Coulter counter based on RPS（resistive pulse sensing） detection. A micro-pipe is used to directly inject liquid metal into the chip, which makes a three-dimensional detection electrode. And the liquid metal electrode is precisely confined in the relevant region by a capillary valve at a micro scale after the solidification. Through the size design of the detection area and the precise control of the electrode position, we have made the C. elegans counting chip. The experiment proves that the method is simple and convenient in manufacturing process, accurate in electrode position, stable in detection, and improved detection signal-to-noise ratio.