We report a systematic study on the dependence of nanowire evanescent wave coupling efficiency on wavelength, cross angle, and core diameter. An $800\mathrm{nm}$ diameter silica taper was used for light launching. Three poly(trimethylene terephthalate) nanowires with $640\mathrm{nm}$ , $790\mathrm{nm}$ , and $950\mathrm{nm}$ diameters were used for light transmission. Five wavelengths (visible, 473, 532, $650\mathrm{nm}$ ; near-IR, 1310 and $1550\mathrm{nm}$ ) were used as transmission signals. The dependence of coupling efficiency was investigated at cross angles from 90° to 0° with a 5° changing step. It is observed that the coupling efficiency is higher for longer wavelength of light, smaller cross angle, and smaller nanowire diameter.