Abstract: The comments issued by the Water Army were repeatability and similarity.A method to find Water armies in weibo based on Text similarity was proposed.Comments are represented by signatures.By indexing the signatures on efficient B-Tree,the whole system had extreme processing efficiency.According to the repeatability and similarity characteristics of the comments issued by the Water Armies,the users which defined as Water Armies had a high number of occurrences when analyzed on the same or similar comments.And then analyzed the comments published by those users,found that those comments were almost similar.Experiments showed that this method could find the Water Armies accurately and effectively.