Ba1-xSrxTiO3 thin films have been deposited on Pt/Ti/SiO2/Si substra by the pulsed ArF laser deposition method. Deposition conditions, such as ambient gas and substrt temperatze, have been optmized to rrxove crystallinepropesty. Fe oelectric p e phasehasbeenobtainod ithe BSTthin filns deposited above 500°C in Q2 gas havingpressure ofabout 13Pa. Using N2O gas instead of O2 gas improved the crystallinity, because highly chemical active oxygen radicals produced due to ultraviolet inadiation of the laser. Doping of Bi ranging around 2% fills of the role of decrease leakage current of BST thin films. Temperature dependence of the dielectric constant (εr) shows a sharp change, peaking aroumd room temperature. The peak point exists below 25°C in the ratio of Ba/Sr=1.1 film, and shills above 50°C in Ba/Sr=5.7 film. When the Ba/Sr ratio is 1.4 the dielectric peak exists near 27°C and is very sharp. The maxinium differentW rate of dielectric constanttversus temperature is the largest in Ba/Sr=1.4 film and is about 100K-1. This value is equivalent to apyroelectric coefficient of 1.8 × 10-7 C/cm2K, which is almost the same as that of LiTaO3 single crystl, a typical pyroelectric material.