1064 nm nanosecond pump pulses and conventional single mode fibers are adopted to generate supercontinuum whose spectrum covers from 700 nm to above 1750 nm. In the fiber′s normal dispersion regime, the spectrum initially shows multi Raman Stokes lines. As pump power or fiber length increases, Stokes energies enter into anomalous dispersion regime and form optical solitons, which make the following spectral broadening to be dominated by soliton-related nonlinear effects. We show experimentally that the supercontinuum generates with 28 m fiber length has flat spectral structure (in less than 3 dB flatness), high spectral density (0.4 mW/nm in average) and single mode output in 1260 nm to 1750 nm regime.