An operating structure of a pilot-operated solenoid valve is provided. The pilot-operated solenoid valve includes a valve body having a main valve orifice and a pilot valve orifice to open and close the main valve orifice. The pilot valve orifice communicates with an accommodating chamber of the valve body. The operating structure includes a knob, an adjustment rod, and a water stop nut. The knob is positioned and fitted to an opening of the accommodating chamber. The adjustment rod is hermetically fitted in the accommodating chamber. One end of the adjustment rod is threadedly connected to the knob, and the other end of the adjustment rod is connected to the water stop nut. The adjustment rod is driven to move axially by rotation of the knob for driving the water stop nut to control the opening and closing of the main valve orifice.