Bismuth layer-structured ferroelectric PbBi4Ti4O15(PBT) thin films were fabricated on Pt/Ti/SiO2/Si substrates by sol-gel spin coating and the effect of lead and bismuth concentration on phase transition, microstructure and ferroelectric property was investigated. Especially, the effect of non-stoichiometric compositions, that is, deficient concentration of Pb and excess concentration of Bi with respect to the stoichiometric composition, was examined. With an increase of lead and bismuth concentration, the pyrochlore phase was suppressed and PBT phase was developed. Large increases of 2P(r) and 2E(c) were also observed as lead and bismuth concentration increased. An improved ferroelectric property could be obtained by inserting a Bi-rich buffer layer between Pt electrode and Pb-rich PBT film. The PBT thin films with Bi-rich buffer layer showed homogeneous grain size distribution, good fatigue endurance up to 1 x 10(9) switching cycles, low relative permittivity of 270 and sufficient 2P(r) values of 15.7 muC/cm(2).