With mode coupling theory and finite element solving method, a photonic crystal fiber (PCF) coupler basing on selective infiltration and its response to bending are investigated. The bended coupler is treated as a straight waveguide by introducing an equivalent refractive index (RI). The coupling wavelength is simulated and the bend sensing characters are analyzed. The coupling wavelength shift has linear response to bending curvature with directional indication; the coupling wavelength is decided by the RI of infiltrated liquid and the diameter of air-holes; while the bending sensitivity is affected by the distance between the infiltrated hole and the fiber core. With these characters, a two-dimensional bending vector sensor is designed based on selectively infiltrated PCF. Two orthogonal air-holes on the cross-section of the PCF are selected to be filled with different RI liquids. The two liquid waveguides couple with fiber coreseparately. The shift of two coupling wavelengths indicates the bending curvature in two orthogonal directions. The bending curvature and two- dimensional direction can be solved simultaneously by inspecting the shift of two coupling wavelengths. The flexible design and controllable fabrication of the sensor has been demonstrated and a promising sensing application could be seen.