We propose an improved design of photonic crystal fiber (PCF) with ultra broadband-flattened dispersion and ultra-low confinement loss in the telecommunication window. The design is considerably suitable for the generation of wideband supercontinuum spectrum. Numerical results reveal that the proposed PCF structure possesses a low dispersion of 0+-1.5 ps/(nm.km) in the wavelengths ranging from 1.134 to 1.805 \mum (approximately 700-nm bandwidth) with a confinement loss of less than 10?8 dB/km. In addition, a nonlinear coefficient greater than 11.47 (W.km)?1 and a dispersion slope of as low as 0.005694 ps/(nm2.km) are obtained at 1.55-μm wavelength. Moreover, a symmetric flat supercontinuum spectrum with a 10-dB bandwidth of 190 nm is achieved in a 3-m-long fiber, verifying the excellent optical features of the innovative PCF.