We studied the crystallization behavior of amorphous PbTiO3 thin film grown at 30$0^{circ}C$ by RF magnetron sputtering on Pt substrate. Crystallization to full perovskite phase was observed after annealing at 475$^{circ}C$, for 9min, without PbO volatilization. The higher the annealing temperature, the shorter the time required for crystallization. The isothermal kinetic study at 475$^{circ}C$ showed that the Avrami constant was approximately 4, which implies that the crystallization can be characterized by isotropic 3-dimensional growth with a constant nucleation rate. The TEM study revealed that the crystallized thin film was composed of very fine (20~100nm) grains oriented randomly without any evidence of 90$^{circ}$domain boundaries.