A moving object detection circuit for detecting movement information of a measured object. The moving object detection circuit includes a mixing circuit, an analog-to-digital conversion circuit, a mixing unit, and a distance detecting unit. The mixing circuit mixed the RF carrier signal and a first analog signal to generate a second analog signal. The first analog signal is generated by a signal reflected from the measured object. The analog-to-digital conversion circuit coupled to the mixing circuit for generating a digital signal according to the second analog signal. The mixing unit mixed an IF signal and a first/second IF carrier signal to generate a first/second signal. The distance detecting unit generated a detection result according to the first signal and the second signal. The detection result is corresponding to a distance between the measured object and the moving object detection circuit.