Terahertz (THz) technology has attracted much attention due to its application potentials in high speed wireless communication, non-destructive imaging, spectroscopy and others. However, the development of the materials for THz modulation is still a challenge. Metamaterials composed of periodic subwavelength structures can precisely modulate the amplitude, phase and polarization of electromagnetic waves, providing some opportunities for designing ultra-compact and high-performance THz devices. THz metamaterials modulate THz based on its resonant behavior. However, the modulation efficiency of Mie resonance and other common resonances is not evident due to the low resonant strength. Fano resonance possesses a more intense resonant strength and is sensitive to external dielectric environment, thus greatly improving the efficiency and sensitivity of THz wave modulation. The optically-modulated all-dielectric THz Fano metamaterial with a high efficiency was proposed based on the mechanism of photogenerated non-equilibrium carriers in a high purity silicon. The results show that the optical pump of near infrared laser effectively modulates the Fano resonant strength via controlling the conductivity of high resistance silicon, and the modulation depth reaches 87%, which is 70% greater than that of Mie electric dipole resonance in the same structure, realizing the efficient modulation of terahertz wave. The preparation method is simple and the modulation effect is obvious. The resonant frequency of Fano metamaterial can be conveniently designed by varying the geometric size of the metamaterial, which provides a possible approach for the high-performance modulation devices in the THz regime.