In the power system of plane, the work point of the carbon-pile voltage regulator is often drifted, so it needs testing and adjusting regularly. A design of a general - purpose carbon-pile voltage regulator automatic adjusting - testing system is presented which improves the original adjusting method. The mathematical model of the system is built up; both the software and the hardware of the adjusting-testing system are designed, simultaneously the result and error of the system are analyzed.