A new type of hierarchical fuzzy system(HFS) is presented in this paper. Outputs in the previous layer which
is called intermediate variables are not used in the IF-parts, but used only in the output of the following fuzzy unit in
this hierarchical fuzzy system, which can reduce the number of fuzzy rules and the parameters to be identified, and the
intermediate variables with little physical meaning can avoid to be fuzzified. Analytic expression of the system is given, and
the approximation ability and its sufficient condition are proved. The simulation results show that the proposed HFS has a
broad prospect of application.

hierarchical fuzzy systems;approximation;sufficient condition