With the rapid development of optical communication technology, the requirement of the size and performance of the modulator are higher. Therefore, an electro-optic modulator based on Aubry-André-Harper (AAH) resonator is proposed in this paper. The device is based on silicon and etched circular air holes to form triangular photonic crystal structure. AAH resonator is introduced into the line defect of photonic crystal. The p-n junction is formed by doping the line defect. According to the carrier dispersion effect of silicon, the refractive index of the substrate plate is changed by changing the modulation voltage, which results in the displacement of the resonant wavelength and achieves the modulation purpose. The Lumerical simulation software is used to analyze the device performance. The simulation results show that the 3 dB bandwidth is 1.01 nm on the device with 9.03 μm length. When the refractive index difference reaches 0.01, Transverse Electic (TE) mode narrow bandwidth modulation with 1 550 nm wavelength can be realized. The insertion loss of the device is 1.33 dB and the extinction ratio is 29.13 dB. The process error has little effect on the device performance. The electro-optic modulator is easy to integrate, small in size and has high extinction ratio, which is of great significance for the development of integrated optical devices.