Ultra-compact TE/TM polarization splitters in LiNbO 3 photonic wires with two parallel LN optical waveguide at 1.31μm wavelength have been presented. The operating principle of the polarization splitter is based on the directional coupling mode and easy to design by using commercial software Optiwave FDTD. Calculated steady-state field distributions indicate that guided lightwaves in both TM and TE polarizations can be spatially separated from different output waveguides ports. The transmittances of TE and TM in the proposed polarization splitter at 1.31μm wavelength are 98.3% and 96.2%, respectively. The bandwidth of TE mode with transmittances more than 93% is greater than 40nm. And that of TM with transmittances more than 90% is greater than 60nm. The coupling length and total length of the device are 39μm and 37μm, respectively. In addition, the dependences of the transmittance on coupling length for TE/TM polarization in the proposed structure are demonstrated, respectively. The simple and compact wavelength splitter is expected to be applied to highly dense LN photonic integrated circuits.