The invention discloses a watermark superimposing method and device of an image. The watermark superimposing method of the image comprises the steps that a seed watermark and watermark parameters are determined, wherein at least one of the watermark parameters and/or the seed watermark are/is randomly determined; a watermark image is generated based on the seed watermark and the watermark parameters; and the watermark image is superimposed on the original image to acquire a watermark protection image. According to the watermark superimposing method and device of the image, the image protected by a random watermark can be acquired; the original image is difficultly acquired through anti-watermark-superimposing; an unauthorized party is effectively prevented from acquiring the original image; and the original image is protected.