We studied the timing and carrier envelope phase synchronization from two independent Yb-doped femtosecond lasers. With the balanced optical correlation method used, timing delay of the pulses from two lasers is detected. Two pulse trains are synchronized through controlling the piezoelectric transducer in one of the laser cavities and the residual timing jitter is 380 as. Different repetition rate locking bandwidths yield different carrier envelope phase signal characteristics. Compared with using the piezoelectric transducer (narrow locking bandwidth), using the electro-optic modulator (wide locking bandwidth) leads excess noise to the carrier envelope phase during the repetition rate locking. The output of the two lasers is coincident in space, enters the balanced detector, and the relative carrier envelope frequency signal is detected. The carrier envelope phase is tightly locked by using an external cavity acousto-optic modulator, and the residual phase noise is 495 mrad. The spectrum coherence of the two lasers is achieved, which is the basis of coherent pulse synthesis.