A facile strategy is proposed for a high-performance electro-optic modulator with an etchless lithium niobate (LN) layer assisted by the silicon resonator metasurface, which pioneers the way to engineer an ultra-sharp spectral line shape via the excitation of quasi-bound states in the continuum (BICs). Meanwhile, strong out-of-plane electric/magnetic fields within the proximity area to the electro-optic layer lead to ultra-sensitive modulations. As a result, only a slight voltage change of 0.2 V is needed to fully shift the resonances and then realize switching modulation between the "off" and "on" states. The findings pave new, to the best of our knowledge, insights in reconfiguration of spatial optical fields and offer prospects for functional optoelectronic devices.