A lattice-based Monte Carlo simulation approach has been developed for studying the behavior of intragrain pores during the intermediate and final stages of sintering. The changes of the microstructures and the resulting properties of intra-grain pores during sintering are easily examined. The sintering behavior such as pore size distribution, average pore size, etc. is in very good agreement with the experimental observations. In addition, the relationships between the number of pores and the average pore volume agree well with theory.