The invention relates to a Z-tangent LNOI electro-
optical modulator capable of improving 
modulation efficiency and an application thereof. The Z-tangent LNOI electro-
optical modulator comprises a substrate, an insulating layer, a 
waveguide core layer, an upper cladding layer, a 
signal electrode and a ground 
electrode, wherein a bottom of the substrate is provided with a groove; the insulating layer is disposed on the substrate; the 
waveguide core layer is arranged on the insulating layer, and a tangential direction of the 
waveguide core layer is Z-tangent; the upper cladding layer is arrangedon the waveguide core layer, is used for forming a 
refractive index difference with the waveguide core layer so as to limit transmission of an 
optical field, and is used as a support structure of an upper-layer 
electrode; the 
signal electrode is arranged at the position, corresponding to an optical waveguide, of the cladding layer and used for applying an 
electric signal to form an electric fieldto perform electro-optical modulation on light in the waveguide core layer; and the ground electrode is arranged in the groove, and an 
electric field between the ground electrode and the 
signal electrode is along an 
optical axis direction of the Z-tangent LN. In the invention, ultra-efficient electro-optical modulation of near 100% of the 
electric field to an 
optical field is realized so that a half-wave 
voltage of the modulator is greatly reduced, and 
power consumption of the modulator is reduced.