Microwave properties of Ba 0.6 Sr 0.4 TiO 3 (BST) thin film have been studied using interdigitated capacitor (IDC) structure in the frequency range from 1 to 10 GHz at room temperature. IDC was fabricated on the c -axis oriented BST film grown by the pulsed laser deposition method. The capacitance of IDC shows high tunability and the quality factor is comparable to the reported values under dc bias voltage from 0 to 40 V. Dielectric constant of BST film was extracted using the conformal-mapping model from the measured data and physical dimensions of capacitors. Calculated dielectric constants depend on the geometric parameter of IDC.