Textured YBCO thin film was grown on a 8000Å-thick single crystalline Pt substrate. In order to get the substrate, a multiple layer, Pt/$SrTiO_3$/BaO was deposited on a YSZ(100) substrate and then Pt/$SrTiO_3$ layer was separated from the YSZ substrate in water. A fine control of temperature for initial deposition of $SrTiO_3$ was essential for the single crystalline growth of 8000Å-thick Pt/$SrTiO_3$ overlayer. It was confirmed by XRD measurements that a single crystalline Pt film and a well textured c-axis normal YBCO film were grown. $T_c$ was about 79K. A brief theoretical calculation shows that YBCO film on the very thin Pt substrate satisfies the conditions for a very sensitive bolometer.