We investigated crystaographic orientation change and microstructural evolution of perovskite $PbTiO_3$ thin films which were deposited on $(111)Pt/SiO_2/(100)Si sbustrate at $500^{circ}C$ by multiple cathode sputtering. The films depostied without PbO buffer layer had(111) preferred orientation and triangular-shaped grains, whereas the films deposited on PbO buffer layer revealed highly c-axis preferred orientatio normal to the substrated and more densely packed rectangular-shaped grains. It was observed that PbO buffer layer selects the (001) preferred orientation and characteristics microstructure of $PbTiO_3$ thin films in the initial growth stage.