The chromium free passivation process of aluminum alloy controls the process quality by detecting the aluminum content, but the existing manual detection methods have low accuracy, low efficiency and poor safety. This system takes PLC as the core, and uses sensors such as PH meter and actuators such as peristaltic pump to automatically complete the detection. It can not only complete the aluminum content detection process and real-time display, but also realize remote interaction through the connection between cloud and mobile phones and other portable devices. It has the characteristics of accurate measurement, environmental protection and use safety, and good scalability.