Abstarct: Discovery of unique properties of carbon nanotubes like mechanical, electrical and thermal properties by Iijima since 1991 has attracted many of researches. These properties cause to use carbon nanotubes in medical application, reinforced in composite material, sensors and resonators etc. Resonators are key components in signal processing systems. Reduction in the size of a resonator enhances its resonant frequency and reduces its energy consumption. For sensors, higher resonant frequency means higher sensitivity. For wireless communications, higher frequency resonators enable the production of higher frequency filters, oscillators, and mixers. CNTs have favorable properties, such as extremely high in-plane elastic modulus, high natural frequency and thermal conductivity. These properties, combined with their nanometer-sized, perfect atomic structure, imply that CNTs have potential applications in nano-electromechanical systems, such as components for high frequency oscillators in sensing and signal processing applications. Meanwhile vibration analysis of carbon nanotubes affects their application as nanoresonators strongly. Previous researches indicate that in the best situation at least one defect is observable in 1 µm of CNTs length. One of the most important defects that occur during growth process is vacancy defect. This thesis presents the effect of vacancies on natural vibration of single walled carbon nanotubes. Zigzag and armchair carbon nanotube with chirality indices (8,0), (10,0) and (6,6) are considered. Vibration analysis for single walled carbon nanotubes with two boundary cantilevered and bridged are considered. Molecular dynamic model and finite element method are used to simulate SWCNTs. Related stiffness is calculated from molecular potential energy. Vacancies’ effect is considered in two conditions, one a vacancy on structure, two scattered vacancies. Vacancies are scattered randomly on SWCNT structure for better simulation of actual condition. Accuracy of modelling is verified by comparing our results of predicting ideal SWCNT natural frequency, with results of previous studies. Results indicate that vacancies affect natural frequency of SWCNTs strongly. Effects of aspect ratio, diameter, distribution of vacancies, and boundary conditions on natural vibration of defected SWCNTs are investigated. Our results indicate that by decreasing aspect ratio and CNT diameter, natural vibration frequency shift increases. Distribution of vacancies affects natural frequency shift. As vacancies approach to the clamped end, natural frequency shift increases.