Abstract-We demonstrate all-optical ultra-broadband tunable wavelength conversion of one-picosecond pulses based on four-wave mixing in a 3-millimeter long dispersion engineered silicon waveguide. In the waveguide, an input pulse with center wavelength at 1600 nm is down-converted by 135 nm (17.3 THz) to 1465 nm. A tuning range of 115 nm (15 THz, from 1465 nm to 1580 nm) of the converted wavelength is demonstrated, while keeping conversion efficiency, pulse shape and pulse width almost unchanged.