Abstract: In this paper,aiming at copy protection of a large number of word documents in network transmission,we use the hamming error correcting coding,IDEA encryption technique,and the digital watermarking algorithm of changing the word document's character size to realize it.This algorithm is on the basis of character's feature coding idea and it realizes the embedding and detecting of text watermarking.And we use the error correcting coding to enhance the anti-jamming ability of watermark.The experimental results show that the algorithm has good hiding effects,good ability of counteracting attacks and good robustness.