The great developments in applied mathematics and computational capabilities facilitate the design and implementation of robust control. Among the real applications are the guided missiles especially the antitank guided missile systems which are commanded to the line of sight (CLOS) against ground and short-range targets. The present work is concerned with improving the performance of an antitank guided missile system belonging to the first generation via robust synthesis of guidance systems. The selection of nominal model is required to design the guidance computer for the system. This paper is devoted to the quantitative analysis to select a nominal plant which used to design a guidance computer that has a successful flight path trajectory against different types of uncertainties. The design and analysis necessitate somehow accurate model with different uncertainties for the system. The flight path is evaluated considering the HIL environment.