Abstract: An optically tunable split-ring resonator (SRR) has been designed on silicon substrate. In the terahertz regime, the samples tunable dual-resonant properties have been obtained through modulation of the conductivity of silicon substrate. We put gallium arsenide (GaAs) into the gap of SRR, and find that the resonant structure of SRR can be changed by adjusting the conductivity of GaAs. Along with the increase of the conductivity of GaAs, the SRR switches the resonance frequency from dual-band LC and dipolar resonance mode to single-band closed-ring mode. Without destroying the SRRs physical structure, the method of changing the conductivity of semiconductor can switch resonant mode and can be implemented in terahertz devices to achieve additional functionalities.