In nanoparticles manipulation with atomic force microscope for modeling exact manipulation dynamics and prevent of damaging nanoparticles, it is necessary to compute critical force. For modeling dynamics and computing critical force that apply to nanoparticles it is necessary to modeling cantilever stiffness and determine sensitive geometrical parameters which are effect cantilever stiffness and critical force. In this paper at first it is investigated on two common different kinds of cantilevers which are V-shaped and dagger cantilevers. For modeling V-shaped cantilever stiffness this cantilever is divided into two parts a triangular head section and two slanted rectangular beams. After that the stiffness of each part is modeled separately and the total stiffness is computed. For modeling dagger cantilever stiffness it is used the same method and cantilever is divided into two parts a triangular head section and a rectangular beam and then the total stiffness is computed. Cantilevers stiffness and critical force in manipulation of biological particles and non-biological particles are very important because of that it is used EFAST sensitivity analyses for selecting suitable cantilever and its parameters. In this paper it has been shown that the dagger-shaped cantilever is more suitable for the manipulation of biological particles.