A 2D/3D dual-mode image sensing circuitry is composed of a photodiode, an active sensing unit, and a pull-down unit. The photodiode is to detect and convert optical signals into electronic signals. The active sensing unit is electrically connected with one end of the photodiode for receiving electronic signals outputted by the photodiode, having an output. The pull-down unit is electrically connected with the output, providing a pull-down path. The pull-down unit has a pull-down control terminal, by which the pull-down unit can be externally controllably switched on/off, for sinking the potential or not to the aforesaid end of the photodiode. In this way, as the 2D mode is switched on, the 3D mode is switched off; on the other hand, as the 3D mode is switched on, the 2D mode is switched off.