Abstract Modern society, the use of batteries more and more things, but the battery does not use a one-time environmental protection and waste of resources, it will pollute the environment. If you use rechargeable batteries so they can effectively change this situation. But how to detect the capacity of rechargeable batteries is also a problem. This paper presents a single-chip microcomputer-based rechargeable battery capacity test design. The circuit can be real-time acquisition of battery voltage, current, calculating the battery has sufficient power; also available through the digital display the necessary information. STC89C51 this circuit to control the use of single-chip, a single-chip STC89C51 circuit, the battery voltage detection circuit, digital circuit, such as display components, to achieve constant current battery discharge, battery capacity to achieve the purpose of detection.