In this paper, 3-D finite element modeling and simulations are carried out to investigate the bending deformation of a single-walled carbon nanotube cantilever biosensor due to mass attached, and addition of a nano-scale particles to the beam tip resulting from the bioparticle detection. In addition, an algorithm for an electrostatic-mechanical coupled system is developed. The computed results are in excellent agreement with the well known electrostatic equations that govern the deformation.