This article designed a circuit for alcohol measurements based on three-electrode biosensor. The circuit system includes MCU controller circuit, potentiostat circuit, scanning voltage circuit and current detection circuit. Potentiostat circuit is designed to keep voltage of working electrode constant. Scanning voltage circuit is to generate reference voltage by DA converter chip. Current detection circuit measure the response current on working electrode. The system can measure the current with the value less than 10-9A, and the degree of accuracy of current can reach below 0.01uA. Different alcohol concentrations are tested based on this system and this system can get the concentration value of alcohol by the corresponding I-t curves.