The present invention discloses methods and systems for measuring the zeta potential of the cylinder's outer surface and the inside surface of the tube. In the measuring cell for measuring the zeta potential of the cylinder's outer surface, the cylinder is placed coaxially inside the reference tube, and the channel existing between the cylinder and the reference tube forms a annular flow channel. Additionally, in the measuring cell for measuring the inside surface of the tube, a reference cylinder is held coaxially inside the tube and a given solution is forced to flow through the annular space between the tube and the reference cylinder.