To explore the applications of carbon nanofibers in passive interference by smoke screen, the integral equation of induced current for carbon nanofibers is established based the electromagnetic field theory. The method of moment (MOM) is used to solve the integral equation. The formulae of scattered field and extinction cross section are derived for carbon nanofibers. By comparing with variational method, our proposed method is proved to be valid. The relationships between infrared extinction cross section of carbon nanofiber and the wavelength, the angle of incidence, the fiber length and diameter are analyzed and calculated.The results provide a theoretical basis for the applicatrion of nanocarbon fiber in infrared smoke interference.