A metamaterial device was designed and fabricated for microfluidic sensing in the terahertz regime, its transmission, resonance and sensing properties were numerically simulated in terms of the Finite Difference Time Domain(FDTD). The influence of polarization direction on the sensitivity of sensor was experimentally investigated by terahertz time-domain spectroscopy system. The experimental result shows that when the resonant metamaterial ring opening direction is parallel and perpendicular with the direction of polarization of the incident THz wave, the refractive index sensing sensitivity can reach 39.29 GHz/RIU and 74.43 GHz/RIU, respectively. The transmission and resonance characteristics of the metamaterials are analyzed by the equivalent circuit model to further clarify the sensing mechanism. This THz metamaterial device has the potential applications in sensing chemical and biological component because it is capable of realizing the refractive index sensing of microliquid (5 μl/mm2) with a high sensitivity.