A digital watermarking system and method is provided. The digital watermarking system mainly includes a storing unit, a background image obtaining module, a pixel determining module, an encrypting module, and a storing module. The storing unit is for storing text information, the text information including textual information and one or more background images. The background image obtaining module is for obtaining one background image to be watermarked from the storing unit. The background image includes plural pixels, and each of the pixels has a brightness value. The pixel determining module is for earmarking the pixel to be adjusted, an initial brightness value of the earmarked pixel being in a predetermined range. The encrypting module is for adjusting the brightness value of the earmarked pixel. The storing module is for storing watermarked text information in the storing unit. Related methods are provided.