Abstarct: In this thesis photoconductivity properties of pure multi – walled carbon nanotubes which have irradiated by xenon and halogen light source, studied. Then with doping alkali mextals potassium and lithium in MWCNTs, their photoconductivity properties have been compaired with pure MWCNTs samples. Photoconductivity properties of the nanotubes irradiated by different light source xenon & halogen were investigated. Result of this study showed that for pure MWCNTs irradiated by xenon light source which is including of ultraviolet spectrum, photocurrent decreases while for doped nanotubes it increases. Moreover photoconductivity for both pure and doped MWCNTs irradiated by halogen light source increased. This study also showed that Photocurrent in potassium – doped carbon nanotubes is more than pure samples. Time – photocurrent behaviors was also for pure and doped samples investigated. This behavior showed that the response time in pure MWCNTs is higher than that in doped samples.