Ba0.7Sr0.3TiO3 (BST) films on Y-cut LiNbO3 substrates are investigated to realize wide-range tunable BST capacitors. The performances of the BST films are improved by the optimal magnetron sputtering conditions. It is found that the permittivity tunability of the BST capacitor reaches 300% under an applied voltage of 5V. Moreover, the film has a high dielectric constant 2700 under an applied voltage of 0 V, and the Q value of the BST capacitor exceeds 3000. The results demonstrate that the BST film on the LiNbO3 substrate has potential as a wide-range tunable capacitor for tunable surface acoustic wave filters.