A terahertz toroidal dipole metamaterial sensor based on mirror symmetric square ring structure with double split is designed and fabricated, and a transmission resonant valley with a Q value of 16.8 at 1.436 THz can be provided by the sensor. The surface current analysis of the structure at resonant frequency shows that the device can rapidly strengthen the toroidal dipole while suppressing the electric dipole and magnetic dipole. As a toroidal dipole metamaterial biosensor, the device has a sensitivity of up to 348.8 GHz /RIU when the analyte thickness is saturated, and can sensitively detect the small changes of the surface dielectric environment. The experimental results have demonstrated the perfect resolutions for discrimination between standard edible oil and gutter oil, indicating its great application prospects in food safety monitoring.