Abstract: The demonstration effect is low in large conference center with multiple projector-screens, because there is no connection between the primary and secondary projector-screens, and the laser pointer on the primary screen could not been shown on the secondary screen. A demonstration method of laser pointer for multiple projection-screens based on camera is proposed in this paper. A connection between the primary projection and the computer screen is built by the camera, and then the point of the laser pointer on the primary projection can be transformed to the one on the computer screen. Based on this, the cursor can be moved and the secondary projection will have the same demonstration effect. The main steps include: (1) compute the homography matrix H between the primary projection and the computer screen by monochromatic projection. (2) extract the point of the laser pointer on the real-time captured image of primary projection. (3) calculate the indicating point on the computer screen base on homography matrix H and control the cursor move to there. Experiment shows that this method can calculate the position of the laser pointer on the computer screen with an error within 5 pixels and track the laser pointer on the secondary screen successfully. This method can both give an unlimited space to the demonstrator and a communication to all the audience.