Abstract: Aiming at the current digital close contact traceability technology which generally suffers from the problems of poor accuracy and low efficiency, this paper proposes a close contact traceability system based on droplet detection, designs a droplet detection terminal, a control center circuit and a traceability software, and uses the laboratory's self-developed droplet sensor, capacitance converter chip and Bluetooth module to design a droplet detection circuit to realize the collection and transmission of droplet information, and a microcontroller , NB-IoT wireless communication module and Bluetooth module to design the control center circuit to realize the collection and transmission of traceability information, and the KVST-DBSCAN clustering algorithm to realize close contact person traceability. Compared with the traditional digital close contact traceability technology, the use of droplet detection to determine the physical distance can effectively reduce the scope of exclusion and improve the traceability efficiency.