Abstract: The corona discharge of the wire is closely related to the space charge. Studying the change of space charge helps to analyze the nature of corona discharge. In this paper, an AC voltage corona cage experimental platform was built, and a series voltage divider circuit was formed by using a grounding capacitor and the stray capacitance formed by the wire and the corona cage, and measured wire voltage and corona cage wall voltage separately. The space charge expression was derived based on the principle of current continuity. The experimental results show that the space charge causes distortion of the grounding capacitor voltage, and the positive and negative half-cycle waveforms have asymmetry. The positive and negative peak values of this waveform were positively correlated with the voltage amplitude and negatively correlated with the voltage frequency and wire radius. The wall voltage of the corona cage could be used as a macroscopic characteristic quantity to reflect the change of space charge. The peak value of space charge, the space charge peak delay and the rate of space charge generation were extracted as low frequency characteristic quantities, and quantitatively analyzed the space charge characteristics of AC corona discharge on wires.