Carrying on the equivalent graduation to all levels of particle content and determining its destruction mode, the author constructs a continual Markov chain model based on the Markov nature of the particle breakage to simulate the particle breakage of coarse aggregates. According to data of the indoor triaxial tests, the criterion of the steady-state is obtained and then a simulation example is given. The results show that, as the time increases, the particle contents of the fourth and third classes are monotonically decreased, and their rate slowed down with time, of which the fourth class is dropped largely, and that the particle content of the second class is first grown with the time and then declined after 15 days. Through the sensitivity analysis of the model, it is stable with the test parameters.