In view of the large diameter and different transmission channels of terahertz beam, the large area terahertz pyroelectric detector and the multi-purpose detector structure were proposed to measure the terahertz beam power, which was transmitted in free space and waveguide. Firstly, a terahertz pyroelectric detector model was established by using the finite element analysis software, and the thermoelectric coupling simulation design was carried out. Secondly, the terahertz pyroelectric detector was developed by using precision grinding and polishing process, micro-nano processing technology of planar integrated circuit, homogenized and peeling process, and grinding wheel slicing technology. Finally, the sleeve and waveguide adaptor mounted on the detector structure were innovatively designed. Theoretical analysis and experimental results show that the terahertz pyroelectric detector designed in this method has the characteristics of low noise equivalent power and high repeatability, and solves the compatibility test problem of terahertz radiation power transmitted in free space and waveguide.