Residual liquid inspection is an important process before filling up in the beer filling line. It aims to inspect that whether there is residual alkali liquid in the inspecting bottles and improve the quality of the beer. At present, manual inspection can’t meet the requirements of high filling speed and high-accuracy inspection. While the automatic residual liquid inspection system at present has some defect such as poor security, low accuracy and reliability. Therefore, this paper proposes a new method for residual liquid inspection which is based on the principle of capacitive coupling and has realized non-contact measurement for residual liquid remaining in empty bottle. The inspection prototype is also designed for detection. In order to further improve detection reliability, the statistical process control method is also introduced in the residual liquid inspection system. According to experiments, it is indicated that this method can effectively improve accuracy, reliability and security of the detection and has high practical value.