An electrical power sharing circuit applied in a computer system, which comprises a central processing unit and a graphical processing unit, the electrical power sharing circuit comprising: a first sense unit, electrically connected to the CPU, for generating a first power value; a second sense unit, electrically connected to the GPU, for generating a second power value; a first control unit, electrically connected to the first sense unit, the second sense unit, the CPU and the GPU, for receiving the first power value and the second power value; and a second control unit, electrically connected to the first sense unit, the second sense unit and the first control unit, for receiving the first power value and the second power value, and providing a first reference value (Pw_Th1) and a second reference value (Pw_Th2) to the first control unit, characterized in that the second control unit obtains a first power ratio by summating first power values and then dividing by a maximum operating power consumption value of the CPU, and obtains a second power ratio by summating second power values and then dividing by a maximum operating power consumption value of the GPU; wherein the second control unit judges the operation as a CPU-dominated operation when the first power ratio is greater than the second power ratio, and judges the operation as a GPU-dominated operation when the second power ratio is greater than the first power ratio; wherein a sum of the first power value and the second power value is a power sum (Pw_CORE) and the first control unit controls performances of the CPU and the GPU according to the first reference value (Pw_Th1) and the second reference value (Pw_Th2); wherein when the operation is judged as a CPU-dominated operation, the first reference value (Pw_Th1) is smaller than the second reference value (Pw_Th2); wherein when the operation is judged as a GPU-dominated operation, the first reference value (Pw_Th1) is greater than the second reference value (Pw_Th2); f wherein when the power sum (Pw_CORE) is greater than the first reference value (Pw_Th1), the GPU is controlled to be entered a low frequency operation mode, and when the power sum (Pw_CORE) is greater than the second reference value (Pw Th2), the CPU is controlled to be entered a low frequency operation mode. a first sense unit, electrically connected to the CPU, for generating a first power value; a second sense unit, electrically connected to the GPU, for generating a second power value; a first control unit, electrically connected to the first sense unit, the second sense unit, the CPU and the GPU, for receiving the first power value and the second power value; and a second control unit, electrically connected to the first sense unit, the second sense unit and the first control unit, for receiving the first power value and the second power value, and providing a first reference value (Pw_Th1) and a second reference value (Pw_Th2) to the first control unit, characterized in that the second control unit obtains a first power ratio by summating first power values and then dividing by a maximum operating power consumption value of the CPU, and obtains a second power ratio by summating second power values and then dividing by a maximum operating power consumption value of the GPU; wherein the second control unit judges the operation as a CPU-dominated operation when the first power ratio is greater than the second power ratio, and judges the operation as a GPU-dominated operation when the second power ratio is greater than the first power ratio; wherein a sum of the first power value and the second power value is a power sum (Pw_CORE) and the first control unit controls performances of the CPU and the GPU according to the first reference value (Pw_Th1) and the second reference value (Pw_Th2); wherein when the operation is judged as a CPU-dominated operation, the first reference value (Pw_Th1) is smaller than the second reference value (Pw_Th2); wherein when the operation is judged as a GPU-dominated operation, the first reference value (Pw_Th1) is greater than the second reference value (Pw_Th2); f wherein when the power sum (Pw_CORE) is greater than the first reference value (Pw_Th1), the GPU is controlled to be entered a low frequency operation mode, and when the power sum (Pw_CORE) is greater than the second reference value (Pw Th2), the CPU is controlled to be entered a low frequency operation mode.