By assembling polymer micro/nanowires, 3D wire structures for photonic integrations were fabricated, including a 2x2 crossed structure, a 3x3 crossed structure, and a parallelogram structure. Optical wave-guiding properties of the 3D wire structures were demonstrated with a measured insertion loss of 0.83 dB, on average, at 650 nm wavelength. Light can be transmitted vertically from one wire to another. Coupling efficiency between adjacent wires is tunable by changing the cross angle and the center-to-center distance.