Аннотация:Driver fatigue is a key factor of accident. To solve the problem, eye tracking method is used to alarm tired drivers. To finalize this procedure, we took driver face images first by using a digital camera, then the images are processed and segmented. Then the horizontal projections of the detected objects in the binary images are analyzed. In this way, eye locations are obtained based on the horizontal projection histogram (e.g. at high peak of projection charts). And horizontal boundaries of eyes are located at the valley points. To determine the valley points, an improved slope algorithm is presented in this paper. We use first order linear difference with five steps to calculate curve slope. As a result, boundaries of eyes can be obtained. And eye pixels can be counted in the eye region. Spirit status of drivers can be detected by analyzing the eye pixel numbers.