Abstract: In order to verify and model checking real-time system,various models have been suggested such as timed tree automata.The theory of timed tree automata is far from perfect now.The classes of languages and their relationship have been discussed.This paper proposes a condition of timed tree automata recognizing language,proves the correctness of its.If a language can not satisfy the condition,it mustn't be accepted by a timed tree automata.It is a potential way to approve a language being a non timed tree reg...