Abstract: A method for controlling a portable terminal by a touch device includes the following steps: connecting the touch device to the portable terminal, and recording a screen resolution of the portable terminal; displaying the same image on respective screens of the touch device and the portable terminal synchronously; resetting respective cursors on the respective screens to corresponding reference points concurrently; detecting an absolute coordinate of the cursor on the screen of the touch device in response to a press operation performed upon the screen of the touch device; calculating a relative displacement between the absolute coordinate and the corresponding reference point; transforming the relative displacement into a corresponding relative coordinate of the cursor of the portable terminal; transmitting the corresponding relative coordinate to the portable terminal over a wireless link; controlling the cursor of the portable terminal according to the corresponding relative coordinate; and resetting the r