Abstract: Based on the experiment of small dynamic bond number on the ground, the free surface oscillation in the marangoni convection of the half floating zone is studied. Two sets of synchronous optical video systems and associated mage processing units are used to observe the displacement oscillation of the free surface radii in two perpendicular cross-sections. The phase difference distribution of oscillation in two profiles along the axial direction is measured. According to the experimental results, there is azimuthal variation, in addition to the oscillation in the radial and exial direction. The basic wave pattern of azimuthal motion and the sensitivity and error of measurement are also discussed in this paper.