The application of computer vision technology to traffic detecting and information collecting is an important subject in ITS (Intelligent Transportation System), and moving vehicle detecting and tracking is the basic part. The further study on this question is carried out systematically in this paper. Taking the natural road as the background, a kind of moving vehicle auto-detecting and auto-tracking method is brought forward. Moreover the software system is designed and implemented. A moving vehicle can be automatically tracked elementarily by using the software system.The main contents of the study include such aspects as follows: (1) The moving vehicle auto-detecting grid arithmetic is studied and presented on the basis of the idea of the image difference arithmetic. The moving vehicle is detected whether or not to enter the field of view by calculating the grid dissimilarity between the current frame image and the reference frame image. DSDR (Dissimilarity Descend Rate) is defined, and by calculating it the position of the moving vehicle in grids can be determined exactly, so the vehicle model image can be saved conveniently. (2) The moving vehicle state forecast linear model in which the system state is characterized by an eight-dimension vector is founded by adopting Kalman filter theory. The forecast model is encapsulated as a class with object-orientated technology. The data members and member functions of the class are also given. (3) The moving vehicle tracking problem is discussed at two conditions: the camera is still and the camera is moving. Under the circumstance that the camera is still, the moving vehicle is tracked by model matching according to the searching strategy that is proved valid by tracking experiment. Under the circumstance that the camera is moving, the tracking rectangular coordinates are founded, and the relationship between the tracking rectangular coordinates and the forecast rectangular coordinates is given. The angle control formula of the camera & pan-tilt-device system is educed with its vision coordinates, which provides theory basis for moving vehicle tracking. (4) The data stream chart of the system is given by making use of the data-stream-orientated design method. The software system is implemented with Visual C++ program language on Windows 2000 platform. With the guidance of the modularization idea, the software system is divided into six modules: image collecting and taking module, image processing module, image displaying module, and so on. This software system can accomplish moving vehicle auto-detecting, state forecasting and auto-tracking elementarily. Some useful practice in moving vehicle video surveillance is done. (5) Last, the composing and the structure of the hardware system are introduced.