Abstract: Carbon nanotubes have been proposed as one of the most promising materials in nanoelectromechanical systems (NEMS). In this paper, using the bistability of single-walled carbon nanotubes, we at first give a prototype design of nanoswitches which can serve as fundamental building blocks for the design of NEMS components or random access memory. The switch may be switched between ON and OFF states by applying electrostatic forces. We then focus on the mechanical behavior of the switch being turned on from off state, that is, a redial compressed single-walled carbon nanotube collapsing into a ribbon-like structure. The molecular dynamics simulation we used is based on second-generation-bond-order potential developed by Brenner. We show that, with the tube diameter increasing from 2 to 5 nm, the energy barrier between the two stable states of a nanotube increases firstly and then decreases. The peak value of energy barrier is reached at the diameter equal to about 3.8nm. This conclusion is very useful to the potential application of the bistability of carbon nanotubes in NEMS. We also investigate the radial elastic modulus of carbon nanotubes and the results show that it is approximately in linear relation with the tube diameter in a double logarithm coordinate system for the tubes with diameters ranging from 1 to 5 nm. Keywords: nanotube; molecular dynamics; bistability; nanoswitch