A touch display panel and controlling method thereof are provided. The touch display panel includes a first substrate, a second substrate, a display medium layer, a first common electrode, and a pixel structure including a pixel electrode and a second common electrode. The first common electrode has a voltage signal. In a display mode, the pixel electrode is provided with a data signal so that a first voltage difference exists between the first and the second common electrodes. The arrangement of the display medium layer varies according to the data signal and the first voltage difference. In a touch mode, the second common electrode is provided with an indication signal whose waveform alternates between first and second voltage values. When the indication signal is at the first voltage value and a second voltage value respectively, a second and a third voltage differences exist between the first and second common electrodes.