Lead-free thin film capacitors, simultaneously possessing a large energy storage density, ultrahigh efficiency and an extra wide working temperature range, are desirable in applications. In this work, A(2)Bi(4)Ti(5)O(18) (A = Ba and Sr) thin films were successfully deposited onto Pt/Ti/SiO2/Si by chemical solution deposition. A large energy storage density (Ure) of 37.1 and 17.2 J cm(-3) and a high efficiency (Z) of 91.5% and 80.8% were achieved in Ba2Bi4Ti5O18 and Sr2Bi4Ti5O18 thin films, respectively. Moreover, these two thin films show excellent thermal abilities under an extra wide working temperature range from -100 degrees C to 180 degrees C. Additionally, high cycling fatigue endurance with a variation of the energy storage density of less than 3.7% and efficiency less than 2.1% after 2 x 10(8) charge-discharge cycles is obtained for these two thin films. These results indicate that A(2)Bi(4)Ti(5)O(18) thin film capacitors have strong potential applications in equipment in harsh working environments.