The intrinsic polarization properties and switchable assembly of ultranarrow phase- and shape-controlled zinc selenide (ZnSe) nanorods were presented. Synthesis of shape- and phase-controlled nanorods was carried out by addition of relatively innocuous zinc acetate and selenourea precursors to controlled ratios of liganding solvents of octadecylamine (ODA) and trioctylphosphine oxide (TOPO) in the temperature range 140-220°C. Nanoparticle shape and size could be changed from spherical to elongated particles by increasing the molar ratio of ODA in the mixed solvent. A simple and switchable approach is adopted for large-scale 3D assembly from 1D ZnSe nanorods by application of a low-magnitude dc electric field. This assembly can be scaled by varying the electrode spacing down to the sub-micrometer scale using more sophisticated electrodes. The ordered rods exhibit polarization perpendicular to their long axis, in contrary to the zinc blende (ZB) random rods.