The present application relates to a new terahertz spectrum analyzer, which adopts a detector based on an NMOSFET gate rasterization structure, a detector based on a Schottky contact rasterization structure, a detector based on an HMET gate rasterization structure, and a detector based on a “wave-to-heat conversion structure”, an NMOSFET detector based on a multi-frequency terahertz antenna structure, and an SBD detector based on the multi-frequency terahertz antenna structure as a core component (i.e. sensor) for electromagnetic wave detection, so that the coverage band is wider. In addition, all circuits can be realized by a common integrated circuit process, so that the terahertz spectrum analyzer proposed by the present application has the advantages of small size, low cost, and low power consumption.