There is provided a pixel circuit for performing analog operation including a photodiode, a first circuit, a second circuit and an operation circuit. Within a first interval, the photodiode detects first light energy to be stored in the first circuit. Within a second interval, the photodiode detects second light energy to be stored in the second circuit. Within an operation interval, the first circuit outputs a first detection signal according to the first light energy and outputs a second detection signal according to the second light energy for being calculated by the operation circuit.