The solid phase epitaxy processes of (100) Si implanted at 77K by 180 keV, 1×1014/cm2 P2+ and 90keV, 2×1014/cm2 P+ have been investigated by using time resolved reflectivity (TRB), Rutherford back scattering and channeling (RBS/C), and cross sectional transmission electron microscopy (XTEM). The difference of TRR spectra between P2+ and P2+ implanted samples annealed at 550℃ is due to the difference in implantation damage of the two different implants. Anomalous TRR spactra for P+ implanted sample can be explained by a model of two direction epitaxial growth from surface layer to amorphous layer and from substrate to amorphous layer.