Abstract: The challenge of touch sensitive interaction lies in detecting the touch action. In this paper, an effective method is proposed for detecting the touch operation on flat surface (e.g. tables and walls), with only one camera, by using the stripes of projection surface and the shadow of fingers. A subpixel accuracy stripes detection method is built up to calculate the stripe offset which can identify a finger touching the surface in a nearly horizon direction. To determine whether a finger suspending or touching the surface with a tilt angle, we take full use of the feature of fingertip to estimate the finger shadow area caused by hovering fingers. The experimental results are shown to illustrate the touch detection rate can reach 96.82% and the processing time is less than 39.24ms.