Behavior-based system (BBS) is a structure built upon behavior components, behavior coordination and behavior fusion. The goal of this paper is to introduce a declarative language especially designed for supporting embedded behavior- based applications. The suggested language adapts the BBS implementation based on fuzzy rule-based systems, fuzzy rule interpolation (FRI) and fuzzy state machines. This case the description of the BBS as a network of behaviors turns to a network of fuzzy systems. The suggested Fuzzy Behavior Description Language (FBDL), is a declarative language for defining FRI rule-bases and a network of fuzzy systems in a unified framework. According to the suggested concept, the FBDL code is "running", as a parameter configuration, directly on a FRI state machine called "FRI Behavior Engine". In an embedded behavior-based application, the FRI Behavior Engine with the parameter configuration fetched from the FBDL code can directly serve the actions according to the observations and the state of the system.