[Display omitted] • LiFe 5 O 8 /Ba 0.6 Sr 0.4 TiO 3 film was integrated on Si substrate using CSD. • An excellent tunability of 71.30% was obtained in LFO/BST film. • The dielectric loss of LFO/BST film was reduced to 0.008. • Establishing an internal field is a good way to realize a better property. It is hard to simultaneously realize the high dielectric tunability and low loss for the single Ba 0.6 Sr 0.4 TiO 3 (BST) ferroelectric film or its composites with the linear dielectrics. In this work, LiFe 5 O 8 /Ba 0.6 Sr 0.4 TiO 3 (LFO/BST) composite films were fabricated via chemical solution deposition method, where the internal electric field could be established inside the film owing to the lithium ions' de-intercalating effect of LiFe 5 O 8 (LFO) layer under the bias field. Thus, we successfully achieved a high dielectric tunability and low loss in the composite films. Owing to the coupling effect in composite films, the dielectric constant remained unchanged at high frequency, while the dielectric loss was reduced to 0.008. An excellent tunability of 71.30% under the bias electric field of −340 kV/cm was obtained in LFO/BST film, which was 41.58% higher than that of BST film. Additionally, the response characteristic of the dielectric constant to the bias field exhibited an asymmetric butterfly curve for LFO/BST composite films. The dielectric tunability in LFO/BST composite films was 19.30% and 71.30% at 1 MHz, under the DC bias field of +340 kV/cm and −340 kV/cm, respectively. These phenomena can be explained in terms of the internal electric field inside the film under the action of the bias field. [ABSTRACT FROM AUTHOR]