For an uncertain discrete event system (DES) modeled as a set of some possible nondeterministic automata, we address robust supervisory control problems. Based on language models, this paper presents the existence conditions of a robust nonblocking (RN) supervisor that guarantees the absence of blocked states in a closed-loop system. We show that an RN supervisor achieves both a given language specification and the nonblocking characteristics of any nondeterministic automata of the set.