Aqueous solution composite electrode（water selective electrode） is a new composite electrode which improves the existing two kinds of electrodes, ion-selective electrode and reference electrode, not only has a great improvement in accuracy, but also simple operation, no professional knowledge, no relevant operation experience personnel can easily use; It also has the characteristics of less sample amount of tested solution, can measure the amount of ions on the surface of the object at the same time, the reference electrode does not need to add electrolyte, liquid interface potential stability, convenient installation, stable performance of the electrode, reliable use and so on.