Lotos is the ISO formal specification language for describing and verifying concurrent and distributed systems. The simulation or execution of complex Lotos specifications is, however, not always efficient due to the space explosion problem of their corresponding transition systems. To overcome this difficulty in practice, we propose in this paper the integration of constraint propagation techniques into the Lotos simulation. Indeed, constraint propagation techniques are very powerful for solving hard discrete combinatorial problems. Experimental tests, we have conducted on the simulation of several specified combinatorial problems, demonstrate the efficiency of integrating constraint propagation into Lotos simulation.