Optimizing production-line layout of IBS plant enhances production time and improves resources'' utilization. Recently, simulation has begun to be applied in construction industry sector. In this book, "Witness 2001" program used to build a simulation model for the production line of pre-cast concrete columns and beams. This simulation model offers the alternatives to modify the production line attributes as the capacity of elements treatment area, number of re-useable moulds and labor, and breakdown of activities. In fact, that imitates a real plant production line. The model provides an opportunity to identify the optimum production line of the suggested layout. This research presents the results of two simulation models; the first is a column model and the second is a beam model. The results involve selection of the appropriate production layout and the required time to produce the assumed amount of columns and beams. Finally, the effect of machineries breakdown and the required resources has been determined in this research.