Abstract: Based on the complex external physical characteristics and the inhomogeneous microstructure of the lunar dust simulant, a sphere super-position model is proposed to calculate its absorptive and scattering radiative characteristics. Four major types of simulant lunar dust particles are identified based on its shape factor and fractal feature, and then the radiative properties of these particles under a monochromatic collimated radiation are studied by using the Monte Carlo ray tracing method. A comparison with known algorithms of nonspherical particles shows a good accuracy of our model. Based on the data from the numerical calculation, the influences of the particle size parameter and the optical constants on the radiative characteristics are analyzed and the phase functions of different particles are calculated. The effect of the particle orientation on its radiative features is also studied by changing the illuminating angle of the incident radiation. Results show that this model can be used not only to study the simulant lunar dust, but also to calculate other large nonspherical particles with even more complex microstructures.