There exist different modeling techniques and advanced tools based on these modeling techniques for modeling and simulation of complex engineering systems. The tools provide flexible, user-friendly environment to researchers and help them in design optimization and performance analysis. The basic aim of this research is to identify optimized modeling methodology and tools for the modeling and simulation of biomechatronic system i.e., lower limb rehabilitation exoskeleton (LLRE). For this purpose, firstly the LLRE is modeled using three different modeling approaches. These include conventional/ mathematical modeling, modeling through bond graph technique and modeling using Simscape ^TM. Modeling through the first two approaches is analytical and graphical respectively while Simscape deals with physical signals while modeling and results in model that is much closer to physical hardware. Secondly, a comparative analysis has been carried out in which dynamic responses of models from different modeling methods have been compared upon certain parameters. This comparison resulted in dynamic responses verification and model validation. Along with that the comparison of different approaches has been carried out and the optimized approach for modeling of bio-mechatronics system such as LLRE is identified. Modeling through Simscape has been identified as optimized approach for modeling of LLRE. This contribution in the field of biomechatronics system control will provide the researchers with an insight about the modeling. This will further pave the way for better model based robust control design. Future work includes comparison of actual hardware dynamic responses with optimized modeling approach.