A proposal for broadband wavelength conversion using four-wave mixing is presented based on a slot waveguide with silicon nanocrystals (Si-nc’s) as the optical nonlinear material. The dispersion of the waveguide is engineered to realize a flat dispersion as well as a small effective mode area for better nonlinear interaction by optimizing the waveguide dimensions. The conversion performance is synthetically analyzed and numerical results show that a bandwidth of over $400\mathrm{nm}$ and an efficiency of $-2.38\mathrm{dB}$ can be achieved using a pump power of $150\mathrm{mW}$ in a $4\mathrm{mm}$ long Si-nc slot waveguide with slot width of $50\mathrm{nm}$ , slab width of $310\mathrm{nm}$ , and height of $305\mathrm{nm}$ .