Abstract: This review introduces in detail the routes to improving the solubility of CNTs in water or organic solvents by noncovalent interaction, i.e., straight dispersion in a single solvent, charge transfer between electron donor and acceptor, the wrapping effect of soluble polymers or cylindrical micelles, etc., and by the covalent chemical modification of the carbon nanotubes, i.e., end-opening, chemical derivitization and side-wall chemical modification etc. Finally, it points out that the focus of carbon nanotube science in future years should be on improving the properties of carbon nanotubes by noncovalent or covalent chemical modification, on extending the application fields of carbon nanotubes by coupling chemical, biological and physical function to carbon nanotubes, and also on a deeper understanding of the reaction theory of carbon nanotubes in solution.