In this thesis, a simulator for unit-load automated storage/retrieval system is developed. The AS/RS is composed of racks, S/R machines, aisles, main conveyor, rack input/output buffer, and system input/output buffer. The simulator has three sub-systems, i.e., input formulation, simulation/animation, and simulation output system. To run the simulation system, the user has to supply the system with the basic AS/RS parameter values. These values can be either obtained through utilizing the design module of input formulation system or directly specified by the user. While simulation is running ; the system performance can be evaluated or analyzed visually by activating the animation system. The simulation/animation system is developed based on the SLAM-II system. Various simulation results can be generated in tableau form or graph.