Abstract: completely new road has been taken to explore modeling of intelligent robot systems from lit-eral and linguistical description to symbolization and further to formalization. Firstly, more complete and exact literal and linguistical description has been established for intelligent robot systems. Then directlythrough symbolizing it in a visualized way, a new kind of structural model, named loop hierarchy model hasbeen proposed and built for intelligent robot systems. Finally, by the utilization of formal language theory,loop hierarchy model has been formalized.Therefore, for the first time, a whole intelligent robot system hasbeen modeled as a kind of context-free grammars in a formalized way and an analytical framework has beendeveloped for modeling of intelligent robot systems. As a result,a new theory,named loop hierarchy modelthoery, has been formed.