Abstract: Based on the molecular structural mechanics approach, a Finite Element (FE) model for varieties of Single Walled Carbon Nanotubes (SWCNT) with Stone Wales (S W) defects is proposed employing the ANSYS Parametric Design Language(APDL) for parametric modeling. To characterize different types of S W defects, a concept of direction angle is introduced. The axial tension and torsion behaviors of SWCNTs with S W defects are simulated, and the effects of type, quantity and array of defects on mechanical properties of SWCNTs are revealed in detail. The results show that the Young’s modulus and shear modulus decrease due to the existence of defects, with individual exceptions which can be explained from the view point of energy. The type and array of defects determine their influence tendency on Young’s modulus and shear modulus; the loss rates of the two moduli are approximately proportional to the amount of defects with the same type and array of defects. The results can guide the estimating of mechanical properties of SWCNTs with S W defects and predicting the defects in SWCNTs.