A power detection and transmission circuit is provided. The power detection and transmission circuit includes a first conversion circuit, a second conversion circuit and a signal coupling circuit. The first conversion circuit is electrically connected to a power supply module to receive an analog input signal, and is arranged for converting the analog input signal to a first pulse width modulation (PWM) signal. The second conversion circuit is arranged for converting a second PWM signal to an analog regenerated signal, and transmitting the analog regenerated signal to a microcontroller, wherein the microcontroller calculates power information of the power supply module according to the analog regenerated signal. The signal coupling circuit is coupled between the first conversion circuit and the second conversion circuit, and is arranged for coupling the first PWM signal to the second conversion circuit and accordingly generating the second PWM signal.