Propagation of the plume formed by pulsed laser ablation of PbTiO3 in an ambient of oxygen and argon was studied by using a CCD camera. Two optical filters with different transmittance bands were used to distinguish the atomic processes in the plume. The results show that, if a strong shock wave is formed, the propagation of the plume formed in pulsed laser deposition in oxygen ambient can be classified into four successive regions from the target to the substrate: (1) the plasma region nearby the target surface; (2) the shock wave forming region in which the interactions between ablated species and ambient oxygen are not chemically reactive; (3) the shock wave propagation region in which the excitations, dissociations, and ionizations, as well as gas-phase chemical reactions between ablated species and ambient oxygen occur; and (4) sound wave region.