The mathematical model of a single-camera virtual computer mouse sensor is established and a field calibration approach to the single-camera virtual mouse is proposed. The mapping from the camera coordinates in working status to the screen coordinates can be calibrated through one media planar target in the camera′s field of view and one virtual target on the screen. Calibrating the single-camera virtual mouse is completed by efficiently establishing an available correspondence between the three-dimensional control point in space and the point of the mouse in the operating system. The proposed approach has an easy operation,and demands no extra costly tools. In the work range of 30 cm and with 50 features from image in 640 pixel×480 pixel,the RMS errors of the control point coordinates in the screen under test are within 3 pixels when the image noise variance reaches 1 pixel. The demo program shows the proposed approach is practicable and is applicable to field calibration for virtual mouse based on the tip of the user′s nose.