Abstract: Modeling the physical behavior of Nano-electromechanical switches (NEMS) is the center of interest for mechanical and electrical engineers. Herein, the abilities of Conventional Adomian Decomposition (CAD) and Modified Adomian Decomposition (MAD) methods in solving the governing equation of NEMS were comparatively evaluated. The pull-in instability parameters of the switch were determined and compared with those of numerical solution. It was found that using conventional decomposition method in solving NEMS problems can lead to physically incorrect results. The values of instability parameters computed by CAD series might converge to the values which differ from that obtained by numerical methods. The inaccuracy became more highlighted in the case of doubly-supported NEMS compared to cantilever one. This shortcoming was not observed for MAD and therefore, modified decomposition method could easily utilize to simulate the pull-in performance of the beam-type NEMS.