It has been an increasing interest in the measurement and control of the carrier-envelope-phase offset (CEO) of femtosecond laser, which leads to an unprecedented progress in both fields of ultrafast laser techniques and frequency metrology. Based on the supercontinuum with a bandwidth of exceeding one octave, we measured and optimized the beat frequency signal by the self-reference technique. A frequency offset of 23 MHz was observed for the Ti:sapphire laser with a power of 500mW and pulse width of 18fs; it corresponds to the CEO of 053π. This work is a significant step toward coherent control of the femtosecond laser.