<p>In response to the increasing demand for high-performance flexible dielectric materials and the fabrication techniques for wearable electronics and energy storage devices, this paper used stereoscopic lithography (SLA) printing technology to prepare epoxy acrylate-based composite films with polyvinylidene fluoride (PVDF) and ionic liquid ([Emim]BF₄). By analyzing the influence of PVDF and ionic liquid on the microstructure evolution and crystalline phase behavior of the flexible composite film, the dielectric property and breakdown performance was investigated. The results indicated that increasing PVDF incorporation promoted the formation of the polar β-phase, where 20 wt.% PVDF was optimal, balancing a 135% rise in relative permittivity (<i>ε</i>′ = 10.39 at 1 kHz) and moderate dielectric loss (tan<i>δ</i> = 0.068). Furthermore, the addition of [Emim]BF₄ accelerated the relative β-phase content, peaking at 52.31% at 15 wt.% [Emim]BF₄. In fact, only 10 wt.% [Emim]BF₄ is needed to achieve an optimal balance (<i>ε</i>′ = 58.29, tan<i>δ</i> = 1.977 at 1 kHz) with improved breakdown strength. However, excessive [Emim]BF₄ will lead to a decrease in the density of the membrane due to porosity and agglomeration, which will lead to a sharp increase in tan<i>δ</i>. This study confirms SLA’s feasibility in fabricating high-performance dielectric composites and clarifies [Emim]BF₄’s regulatory role in PVDF phase transition and composite properties, providing a basis for flexible dielectric material design for flexible sensors and energy storage devices.</p>