Abstract: Terahertz modulator plays an important role in the development of terahertz technology. Optical transmission efficiency of subwavelength metallic hole arrays can be much higher because of the excitation of surface plasmon polaritons, and a higher modulation depth could be obtained by using this structure. A terahertz modulator based on subwavelength metallic hole arrays controlled by optical pump was demonstrated. Firstly, the principles of our sample were researched. Secondly, two -dimensional subwavelength metallic hole arrays were fabricated on semi -insulating GaAs substrate. Lastly, utilizing the terahertz time domain spectroscopy system, the transmission of terahertz radiation through subwavelength hole arrays was measured. Experimental results show that extraordinary optical transmission is excited by subwavelength hole arrays, and optically pumping reduces the terahertz transmission. A higher modulation depth is obtained at special frequency. This research can be the reference to the design and fabrication of terahertz modulator with high modulation depth.