Abstract: A new layered embedding method about text watermarking based on the empty word is presented.To improve the robustness of the algorithm，this paper makes fully use of the advantage of the syntax rules of the empty word to design a kind of layered text method，which has been realized by using the secret key to arrange the rules forming several layers.The layered text method can handle the text as a solid structure，and the embedding data have preferable robustness.

Key words: text digital watermarking, empty word, syntax rule, layered text, robustness

摘要： 为了提高文本数字水印的鲁棒性，需确定具体在载体的哪些部位进行映射层替换，根据虚词结构变换规则提出了一种定位层分层的思想。通过将中文文本按照虚词规则分组，再利用密钥对规则进行随机组合，将文本根据可嵌入水印的关键字动态分层，使文本形成一个多层的立体空间，在各层之间嵌入相关的数据，从而使嵌入的数据形成一个立体构架，增强了水印的抗攻击能力。

关键词: 文本数字水印, 虚词, 语法规则, 文本分层, 鲁棒性