Abstract: Photoelectric measurement is an important basic technology in studies of terahertz radiation. This paper first describes the principle of operation of two terahertz quantum devices and their latest development, followed by an introduction to their applications in pulsed light power measurement, fast modulation and direct detection of terahertz light, optical polarization conversion and measurement, terahertz fiber loss measurement, and related test systems. Finally, the characteristics and advantages of photoelectric measurement techniques based on terahertz quantum well devices are summarized, and future developments assessed.