To characterize a wide-band and high-absorption terahertz radiometer, it is necessary to study the properties of the absorbing coating material. First, we simulated the absorption rates of common absorbing materials to find materials that have high absorption in terahertz range. Further, we mixed silicon carbide and 3M black lacquer to increase the absorption rate of the coating. In addition, we simulated the variation in the internal particle size of the coating. Finally, the mixed coating was prepared based on the simulation results, and the samples were measured using the terahertz time-domain spectrometer. The measurement results show that the spectral absorbance of the mixed coating is greater than 0.99, which is basically consistent with the simulation results.