隨著科技的進步，許多影像檔案均已透過數位化而成為數位影像。由於數位影像具備容易複製及散佈的特性，因此常常衍生出數位影像智慧財產權的爭議問題。為了解決此問題，近年來許多數位浮水印機制相繼被提出，其作法就是在數位影像之中，藏入足以辨識影像所有權的數位訊號。本文中將提出一個以小波轉換為基礎的灰階數位浮水印機制，為了提升浮水印的強韌性，我們將浮水印的灰階值轉換為三種不同重要性的位元，並以不同的方法將此三種位元藏入原始影像中，使較重要的位元資料能得到較佳的保護，而影像的破壞程度則控制在人眼所無法察覺的狀態之下。由實驗結果顯示，本研究所提出的方法對於一些常見的影像攻擊具有相當程度的強韌性。With the explosive growth of digital technologies, more and more images are transformed into digital formats. Therefore, it is very easy to duplicate or distribute digital images in an unauthorized manner. Recently, more and more watermarking schemes are proposed to protect intellectual property rights of digital images. However, only a few of them take into account the issue of gray-level watermarks. This paper proposes an ownership protection scheme based on discrete wavelet transformation (DWT) for gray-level watermarks. To embed a gray-level watermark, we distinguish the gray-levels of the watermark into three kinds of bits according to their importance levels, and embed them into the original image by different methods. Thus, we can increase the survival rate of significant bits under attacks. In addition, the scheme requires neither the original watermark nor the original image during the ownership identification phase. Experimental results show that our scheme can resist many common attacks.