Ultrabroadband spectrum is necessary for generation of ultrafast laser pulses; however, the extent of broadening the spectrum by its own nonlinear effect, such as self_phase modulation or cross phase modulation etc., is always limited. An easy way to broaden the spectrum to an octave is synthesizing the spectrum of its second-harmonic and the spectrum of itself. In this paper, influence of carrier_envelope phase on the synthesizing of two laser pulses is studied.