Fixed Interfacial Multiscale Method (FIMM), a concurrent multiscale model is developed for mechanical analysis of solid nanostructures at the finite temperatures. A direct link between the nano field atoms and macro field nodes using the local atomic volume displacements associated with every macro field node in their common zone has been replaced with the previous methods. FIMM leaves negligible relative motion of atoms in every atomic volume by moving the interface into the macro part. A nano plate in extension and a nanorobotic manipulator have been simulated for comparison. The responses have been compared with the results of semi continuum approach, Molecular Dynamics (MDs), a developed simple Coarse Grained MD (CGMD) and two recently developed multiscale methods. Comparisons show that FIMM is at least 450% better than other methods in numerical cost, and it is also more accurate than other multiscale methods.