PbBi₄Ti₄O₁₅ (PBT) and Pb₂Bi₄Ti₅O₁₈ (P2BT) thin films were fabricated on Pt/Ti/SiO₂/Si substrates by solgel method, and their ferroelectric properties were investigated. Two processes were examined for the preparation of PBT thin films. In the process which used Bi-acetate as a starting material, the single PBT phase thin films could be obtained by inserting a Bi-rich buffer layer between the Pt electrode and the PBT film. In the other process which used Bi-Ti complex alkoxide, the PBT single phase was obtained without the buffer layer. P2BT thin films prepared by the latter process showed about two times larger remnant polarization (2P_r) values of 12μC/cm² compared with 2P_r=7μC/cm² for the PBT thin film, coinciding with the tendency reported for single crystals. Both the PBT and P2BT thin films showed good fatigue endurance up to 1×10⁹ switching cycles.