Temperature-insensitive dielectric properties of nanograin size Ba0.7Sr0.3TiO3 thin films were grown on LaNiO3/Si substrates by rf magnetron sputtering. Scanning electron microscopy and X-ray diffraction investigations show the grain size is about 25 nm. The thin films with nanograin size have much better temperature stability of dielectric properties. The dielectric constant and loss tangent varied slightly as temperature increased from -60 degrees to 60 degrees C. The tunabilities were stable around 15.5% at 50 kV/mm and the temperature coefficients of capacitances relative to the capacitance value at 0 degrees C were all about 2 x 10-4/degrees C during this broad temperature range.