A method and a system for actively detecting and recognizing a placard are provided. In the present method, an image capturing device is moved according to a maneuver rule, wherein the image capturing device captures an image continuously during the movement. Then whether a placard exists in the image or not is determined. If a placard exists in the image, a content of the placard is identified and a corresponding action is executed. The method repeatedly processes the foregoing steps to further continuously move the image capturing device and determine whether the placard exists in a newly captured image so as to achieve a purpose of detecting and recognizing placards actively.