A novel single-polarization single-mode photonic crystal fiber (SPSM-PCF) design with two arrays of four lines of semiminor-axis-decreasing elliptical air-holes is proposed. The proposed SPSM-PCF characteristics are investigated by using a full-vector finite element method (FEM) with perfect matched layer (PML) boundary conditions. The modal birefringence of the proposed SPSM-PCF is as high as 2.752×10-3 at the wavelength of 1.550 μm and the beat length is 0.564 mm. The confinement loss of the x-polarization mode is as low as 0.139 dB/km, whereas the loss of the y-polarization mode is as large as 16.890 dB/km. Compared with the case of x-polarization mode, the y-polarization mode can be suppressed with a shorter fiber length. The numerical aperture is 0.415, the effective mode-field area is 3.667 μm2, and the nonlinear coefficient is 28.740 (W·km)-1 at the wavelength of 1.550 μm. The total dispersion profile of the SPSM-PCF is dispersion-flattened with the wavelength range from 1.347 to 1.691 μm. This dispersion property makes the proposed SPSM-PCF useful for various applications such as supercontinuum spectrum generation and pulse transmission. The spectral region of input light for SPSM operation is as wide as 600 nm. It indicates that this is a good solution to realize broadband dispersion-flattened SPSM operation.