In the image processing research topics, the technology of how to instantly detect human body within a moving region has always been a hot research topic. In recent years, due to the rapid growth of the development in computer hardware, the detecting of the existence of human body via image processing systems has led to a significant decrease of time usage. In this research, QT platform combining with OpenCV library is applied to implement the detection of human body within an indoor moving region. The system contains three components, image capture, image pre-process, and environment determination. First of all, video image is captured via a webcam. Secondly, image pre-process is used to obtain moving pixel area by Background Subtraction in order to conduct smoothing filtering and image binarization. Finally, moving objects are determined by calculating the variations within an image moving region. The results whether moving objects in an indoor environment are detected will show on the left top corner of the screen.