The invention discloses a hydrophobic-modified polyethyleneimine and application thereof as a protein carrier. The structural general formula of the hydrophobic-modified polyethyleneimine is disclosed in the specification, wherein n is any natural number ranging from 5 to 20, and X is Cl, Br or I. The hydrophobic-modified polyethyleneimine can be compounded with protein to form stable nanoparticles, and thus, can be used as a protein carrier. Compared with the prior art, the hydrophobic-modified polyethyleneimine disclosed by the invention has strong protein binding force, can carry antigen protein, can be recognized by antigen presenting cells, and can initiate immunoreaction; and meanwhile, the hydrophobic-modified polyethyleneimine enhances the antigen cross-presentation effect, obviously lowers the cytotoxicity, is beneficial to enhancing the immunotherapeutic effect, and is an excellent therapeutic tumor vaccine nano carrier system.