In recent years, many cases of water pollution have been caused by industrial wastewater. Industrial wastewater containing heavy metal pollution is discharged into the groundwater, causing land and environmental pollution and affecting human health. Hence, the development of a miniaturized water quality detection system (WQDS) to protect water resources is of great urgency. A miniaturized WQDS has the advantages of multiple parameter detection, continuous monitoring, miniaturized dimensions, high sensitivity, and accuracy. The representative water quality parameters monitored by the WQDS were temperature, pH, electrical conductivity, and copper ion (Cu2+) concentration. In addition, fluorine-doped tin oxide (FTO) was substituted for indium tin oxide (ITO) in this study to fabricate an improved pH-sensing module that reduces the interaction between subsystems, improves the measurement accuracy, enhances convenience, and reduces the manufacturing cost of the sensor chips. Electrodes combined with FTO conductive glass were designed and fabricated to achieve the miniaturized WQDS as a system on a chip. The miniaturized WQDS exhibits good potential for the precise detection of various water quality parameters and for application in the water-monitoring field.