Nanowire stiction is a crucial bottleneck for the development of M/NEMS devices.We present a model of a nano-beam stuck to the substrate in consideration of both surface elasticity and residual surface stress.The critical detachment length can be derived from the transversality condition using the variational method.The effects of the surface parameters on the adhesion of the nano-beam are discussed in detail.These analyses provide some suggestions for engineers in the design and fabrication of more accurate M/NEMS instruments.In the bottom-up approach,nanowires and nanobelts are widely used as the building blocks of micro/nano devices,such as micro-sensors,resonators,probes,transistors and actuators in micro/nanoelectro-mechanical systems (M/NMES).[1-3] Unfortunately,the stiction failure caused by spontaneous adhesion between M/NEMS structures has become a major limitation to push better application of these novel devices and this problem has been highlighted as a hot topic in the past decades.[4,5] The main reason of stiction is that in the small spacings,slender structures with high compliance are easily brought into contact with a substrate with strong surface energy.