The increasing popularity of the internet means that digital multimedia are transmitted more rapidly and easily. There is also a greater focus on intellectual property and copyright protection. To prevent piracy and other illegal activities, watermarking is a technique used to protect media data on the internet. An effective watermarking system based on a quantization index modulation (QIM) algorithm in the frequency domain is proposed to achieve copyright protection. The advantages of this approach are that it resists high JPEG compression ratios and maintains good image quality. The procedure consists of two steps: design of a robust embedding mechanism, and embedding and detection of the watermark. In the first step the robust embedding points and values for each image in the JPEG compression are identified. In the second step the QIM algorithm is used to insert a watermark into the image, and then a secure key is recorded. For detection, the embedded watermark is easily extracted using the secure key. Experiments demonstrate that the proposed technique can survive JPEG high compression ratios with good invisibility and robustness.