The scheme for synchronizing Ti:sapphire femtosecond laser and Nd:YVO4 picosecond laser is discribed. Sub-ps jitter is obtained, based on which broad-band femtosecond blue-light laser of 460nm is generated through mixing two laser pulses in the BBO crystal. The technique not only shows a general way of synchronizing lasers of completely different wavelength and pulse width, but also demonstrates a new scheme for generating ultra-short laser with new wavelength through nonlinear frequency mixing.