A photo-sensing pixel circuit including a photo-sensing part, a transfer transistor, a plurality of adjustment transistors, and an output circuit is provided. The photo-sensing part senses a light source and generates a corresponding number of electrons. The transfer transistor coupled to the photo-sensing part has a floating node and converts the electrons generated by the photo-sensing part into a voltage signal. The adjustment transistors have a first end and a second end, wherein the first end is coupled to a power supply, and the second end is coupled to the transfer transistor via the floating node. The output circuit coupled to the transfer transistor outputs a sensing signal according to the voltage signal, wherein the sensing signal is corresponding to the brightness of the light source. The adjustment transistors operate in at least two operation modes. Different numbers of the adjustment transistors are turned on in different operation modes.