Abstract: Three-dimensional barium titanate (3DBT) ceramic network was prepared by sol-gel method using cleanroom wipers as template. Different contents of boron nitride (BN) nanosheets/polyvinyl alcohol (PVA-BN) solution were reversely introduced into the 3DBT network, resulting in flexible 3DBT/PVA-BN composite dielectric film. The study shows that PVA solution can be effectively embedded into 3DBT framework via reverse infiltration, endowing the material with excellent flexibility. The mass fraction of 3DBT in a saturated 3DBT/PVA-BN composite is about 27% (volume fraction 6.9%). What's more, the 3DBT/PVA-0.50%BN system exhibits comprehensive dielectric and energy storage performances. The dielectric constant and energy storage density of 3DBT/PVA-0.50%BN composites are 18.1 (at 1 kHz) of 1.24 J/cm³ (at 90 kV/mm), being 1.74 and 3.54 times higher than those of traditional 27% nano-BT/PVA composite, respectively. In addition, the obtained 3DBT/PVA-BN dielectric film possesses better thermal stability, implying good application prospects.