The invention provides a linear reflection-type electro-optic phase modulator. The modulator comprises a substrate, an optical waveguide, a modulating electrode, high reflecting film and a circulator,wherein the substrate is rectangular; a linear groove is formed in one side of the substrate, and the optical waveguide with the structure same with that of the linear groove is embedded in the linear groove; the high reflecting film is arranged at one end of the optical waveguide, and the circulator is perpendicularly arranged at the other end; the modulating electrode comprises a positive modulating electrode and a negative modulating electrode which are respectively parallelly arranged at the two sides of the optical waveguide, and phase modulation is achieved; the modulator adopts electro-optical crystal or organic matter as the substrate, and the electrooptical effect of the electro-optical crystal is utilized to change the refractive index of materials so as to achieve the phase modulation; the waveguide end surface of the optical waveguide is coated with the high reflecting film, and light beam reflection is achieved; the positive modulating electrode and the negative modulating electrode are applying and acting passages of a modulating signal; the provided linear reflection-type electro-optic phase modulator can reduce half-wave voltage under the premise of not increasingthe length of the modulator, the modulator size is reduced, the modulator is beneficial for integration, the practicability is good, and actual application value is achieved.