Metamaterials have the properties of sensitivity and robust promising applications for sensors. The microfluidic channels can help to detect some analytes with high absorption, and the channel can conveniently transform analyte to sensor’s sensitive area, which means microfluidic sensors need small volumes of analyte. Here, a microfluidic sensor based on metamaterial with a hollow metal shape has been proposed. In this structure, the channel is naturally formed by the gap of metal. This design style can enormously improve the sensor’s sensitivity. The feature resonance peak is ~23 GHz, and the numerically calculated sensitivity is ~132 MHz/RIU. Hence, the proposed structure paves a sensitive and robust way for small volume, high absorption coefficient analyte.