A particle superposition model combined with a Monte Carlo ray tracing method, which is used to study the radiative characteristics of large nonspherical particles, is proposed. The goal of the model is to provide a new approach that not only allows the modeling of large irregular particles of arbitrary shape but also possesses a clear and systematic basic structure that is easy to program. A detailed flow chart and algorithm description are provided in the paper. The data characteristics of four types of irregular particles were calculated and analyzed. The comparison showed that this particle superposition model can be used to calculate the radiative properties of large irregular particles with good accuracy, while at the same time remaining general and extendable to many applications, thus providing a new way to study nonspherical particles.