This study design a novel power detector based on three-dimensional porous graphene (3DPG) and cholesteric liquid crystal microcapsule (CLCM) to measure high-intensity THz waves. The 3DPG is characterized by its high absorptivity, which is more than 97% at the frequency of 0.5-1.5 THz. The thermochromic properties of temperature-supersensitive CLCM are used for visual quantitative study of the THz power under steady state condition. The THz power intensity is as high as 2.77×10 ² mW/cm ², where the minimal detectable THz power is only 0.009 mW. Further analysis reveals that there is a linear relationship between the THz power and the Hue value of the CLCM after the 3DPG is sputtered with a small amount of gold nanoparticles. The visual detector is simple, portable, inexpensive, efficient, and practically applicable. Further, it can be used in THz system alignment and beam analysis as well as THz imaging and sensing.