The PVDF thin film was prepared on PMMA sublayer. Compared to the PVDF on Si wafer, the PMMA layer shows great influence on the crystallization of PVDF under quenching thermal treatment. When the PMMA layer is thinner than 90 nm, mixture of alpha- and beta-crystals form. Pure beta-crystals are obtained when the PMMA layer is around 90 nm. With further thickening of the PMMA layer, pure beta-crystals always form but with a decreased crystallinity. The nanodomains and needlelike morphology of beta-crystals is observed. Moreover the formation mechanism of beta-phase on PMMA interface is clarified. The hydrogen bonds at PVDF and PMMA interface is formed adopting the perpendicular orientation, which serve as the key role to induce beta-PVDF. The amount of beta-PVDF is not only determined by the interaction of PMMA and PVDF at interface, but also the diffusion extent of PMMA into the PVDF layer.