A three-dimensional simulation method based on the Monte Carlo algorithm for the formation of microstructures in ceramics was proposed to control the microstructures in the sintering process. A method that takes into account real time in considering the diffusion rate as a microscopic rate constant can be used to discuss quantitatively the relation between the evolution of microstructures and the operating parameters during sintering, though the general Monte Carlo algorithm can not include time as a parameter. The simulation results from the sintering behavior of the alumina particles consisting of grains, pores and grain-boundaries clearly illustrated the sintering process that densities with grain growth and migration of grain-boundary. The validity of the proposed method which relates real time and Monte Carlo Step was confirmed by the agreement of the simulated values, which were calculated for the heating, sintering and cooling processes according to the experimental condition, with the experimental ones. It was clear quantitatively that the effects of heating rate, sintering temperature, particle size distribution and packing state of particles on the formation of microstructures with pore migration by the simulation carried out in various conditions. The information obtained from the proposed simulation method makes it possible to optimize the sintering conditions.