The theory, concepts and applications of blackbody cavities were introduced in this paper. Characteristics of a new kind blackbody cavity with large aperture which can be used as standard radiant source in infrared imaging system were discussed. The bottom of blackbody cavities was grooved with homocentric cycles in order to increase its intrinsic emissivity. The effective emissivity ϵa(r) of the bottom of the cavity were analyzed and calculated by combing the integrated equation method and the Monte Carlo method. For large number of Monte Carlo simulation, rejection Sample method was used to simulate the Monte Carlo probability model constructed in order to reduce the calculating time. The cavity characteristics have been further proved via testing the consistency and stability of the temperature field. The characteristics of this kind of heat pipe blackbody cavities with large aperture have been authenticated.