Terahertz mixers can mix the original signal with the intrinsic signal and transform the frequency to achieve spectrum detection, super-resolution imaging, and highly sensitive detection of astronomical signals, which have important potential applications in terahertz spectrum identification, terahertz security inspection, and radio astronomical detection. First, this paper introduces the basic principle, classification, and main technical scheme of terahertz mixer. Second, according to the application requirements of ultra sensitivity, high frequency, intermediate frequency broadband, and miniaturization integration of terahertz mixers, the global development trends in the design and manufacturing technology of terahertz mixer are analyzed. Finally, the applicability, technical challenges, and possible solutions of terahertz mixers are summarized to elucidate the technical characteristics of three types of terahertz mixers and identify the technical development trends.