Yuan Zhoumeng, a member of the Literature Retrieval Professional Committee of China Criminal Science and Technology Association and a technical expert of Zhejiang Provincial Procuratorate, said that since it is a forgery, there is little possibility of leaving no trace, and the handwriting has disappeared, but writing requires hard work, which will more or less leave an indentation on the paper, which will destroy the fiber of the paper. The remaining writing marks can be recovered by lighting at a specific angle or using special instruments. Even if the handwriting is very weak and the traces are difficult to find, there are other means in criminal investigation. Although the unstable chemicals in the ink are decomposed into colorless substances, these invisible components remain on the paper. We can find these invisible substances and find writing traces with the help of criminal investigation technology.