An optical pumping terahertz modulators based on silicon pyramid structure is presented. First the micro-scale pyramid structure is etched on high resistance silicon by chemical etching. Then the reflectivity and the terahertz modulation performance of the structure are studied experimentally. Experimental results indicate that pyramid structure can effectively reduce the reflectivity of laser, improve the utilization of laser and significantly increase the modulation depth by increasing the area of the terahertz wave modulation, and the modulation depth is above 90%. This modulator can work at very low laser power and has the characteristics of wide-band and large amplitude modulation, which has important application value in terahertz imaging and communication field.