This paper proposes a technique of image content authentication based on the Laplacian Pyramid to verify the authenticity of image content. First, the image is decomposed into Laplacian Pyramid before the transformation. Next, the smooth and detail properties of the original image are analyzed according to the Laplacian Pyramid, and the properties are classified and encoded to get the corresponding characteristic values. Then, the signature derived from the encrypted characteristic values is embedded in the original image as a watermark. After the reception, the characteristic values of the received image are compared with the watermark drawn out from the image. The algorithm automatically identifies whether the content is tampered by means of morphologic filtration. The information of tampered location is p resented at the same time. Experimental results show that the proposed authentication algorithm can effectively detect the event and location when the original image content is tampered. Moreover, it can tolerate some distortions produced by compression, filtration and noise degradation.