As a special periodic structure, sub wavelength gratings have made important progress in filters, reflectors, couplers, sensors and so on. Among them, the non-uniform grating has a great degree of design freedom, which enables it to have the characteristics of wide bandwidth and high reflectivity in terahertz range. Moreover, different grating constants and filling factors will lead to high selectivity in frequency spectrum, thus achieving tunable reflectors. In this paper, a non-uniform, silicon-based grating was designed and fabricated, and its reflection characteristics were measured by terahertz time-domain spectroscopy in reflection mode and calculated by finite element method. The results show that the non-uniform, high-selectivity, silicon-based grating not only has the advantages of wide frequency band and high reflectivity, but also has the characteristics of simple structure, small size, easy fabrication and large process tolerance.