A human lung cancer marker N3G4, and use of the same as human lung cancer marker is disclosed. Hybridoma cells which produce anti-N3G4 monoclonal antibodies, and the secreted monoclonal antibody LC128, and use of LC128 for the preparation of a diagnostic agent for lung cancer are also disclosed. Kits for in vitro diagnosis comprising the monoclonal antibody LC128 and methods for detecting tumor markers in lung tissue by using the monoclonal antibody LC128 are also disclosed.