An active device, a pixel structure, and a display panel are provided. The pixel structure includes a scan line, a data line, an active device, a gate insulating layer, a pixel electrode, a capacitor electrode, and a capacitor dielectric layer. The active device includes a gate, a channel, a source, and a drain. The gate is electrically connected to the scan line. The source is electrically connected to the data line. The gate insulating layer is disposed between the gate and the channel. The pixel electrode is electrically connected to the drain. The capacitor electrode is located on the gate insulating layer. The capacitor dielectric layer is located between the capacitor electrode and the drain.