Tissue-motion is an important physical parameter that can be considered in discussing the strength of artery pulsation of newborn baby for pediatrics diagnosis. In this paper, we have used optical flow technique to determine the tissue-motion velocity quantitatively in cranial ultrasonogram of newborn baby. We have estimated the tissue-motion by using gradient-based optical flow method and then the time variant tissue motion velocities are analyzed by using Fourier transform. Strong pulsation is observed in the harmonic frequency of tissue-motion that has a relation to the heartbeat frequency of a newborn baby.