This invention involves structure and fabrication method of a black silicon-based MEMS thermopile IR detector. The high-performance black silicon-based MEMS thermopile IR detector includes a substrate; a releasing barrier band on the substrate; a thermal isolation cavity constructed by the releasing barrier band; a black silicon-based IR absorber located right above the thermal isolation cavity; a number of thermocouples are set around the lateral sides of the black silicon-based IR absorber. The thermopiles around the black silicon-based IR absorber are electrically connected in series thus to form a thermopile. Metallic electrodes are located beside the electrically-connected thermopiles for signal output. The cold junctions of the thermopile are connected to the substrate through the first thermal-conductive-electrical-isolated structures, the heat conductor is located at the lateral sides of the thermal isolation cavity. The hot junctions of the thermopile are in contact with the IR absorber through the second thermal-conductive-electrical-isolated structures, and the second thermal-conductive-electrical-isolated structures are located above the releasing barrier band. The structure of such detector is simple, and it is easy to implement and can also be monolithically integrated. Such detector has high responsivity and detection rate, and is CMOS-compatible, thus can be used widely in a safe and reliable manner.