An electrical power sharing circuit applied in a computer system includes first and second sense units and first and second control units. The first and second sense units are electrically connected to a central processing unit (CPU) and a graphical processing unit (GPU) of the computer system and thus generate first and second sense values, respectively. The first control unit is electrically connected to the first and second sense units, the CPU and the GPU and receives the first and second sense values. The second control unit is electrically connected to the first and second sense units and the first control unit, receives the first and second sense values and provides a reference value to the first control unit. The first control unit controls performances of the CPU and the GPU according to the reference value.