The invention discloses a metal polishing solution, and belongs to the field of polishing solutions. According to the metal polishing solution, porous silicon dioxide is prepared by taking boron mud as a raw material, and has a fluffy structure; a lot of disordered slit holes or accumulation is formed; the surface of a sample is cut, and the sample is gradually ground and polished into a mirror surface; a silane coupling agent is used for modifying; the silane coupling agent is attached to the surface of the porous silicon dioxide, and can form a buffering effect in a polishing process, so that indentations are reduced and the aims of reducing mechanical damages and reducing the surface roughness are realized; silane has very good permeability, and can be used for accelerating matter transferring, so that the polishing efficiency is improved. By adopting the metal polishing solution disclosed by the invention, the problems that a silicon dioxide polishing solution is commonly used in current metal polishing and has a relatively good surface effect, but the efficiency is low and corrosion defects are easily generated on the surface of the metal after overlong polishing are solved.