An electrostatic detecting system and an electrostatic detecting method for detecting the static electricity generated at an active surface of a substrate are provided. The electrostatic detecting system includes a sensing apparatus and a signal processing apparatus. The sensing apparatus is disposed at least adjacent to a back surface opposite to the active surface of the substrate, for measuring the static electricity generated at the active surface and generating an initial electric signal. The signal processing apparatus is electrically connected to the sensing apparatus, for receiving the initial electric signal and correcting the initial electric signal based on a voltage compensation value to obtain a final electric signal.