This paper addresses the problem of the design of controller for fuzzy semi-Markov jump systems with hidden modes against the incomplete information on probability density functions of sojourn time.Two ubiquitous circumstances in practice are taken into account,which are often ignored in other related work:(1)the phenomenon that system modes cannot be accessed entirely is considered proactively;(2)finitely accessible information on probability density functions is studied in this paper.By virtue of hidden semi-Markov chain,the underlying systems are modeled as hidden semi-Markov jump systems,which are more general than semi-Markov jump systems.Sufficient conditions on the existence of desired accessible-mode-dependent fuzzy controller are derived such that the fuzzy hidden semi-Markov jump systems is mean square stable.Based on the emission probability matrix,the presented control policy overcomes the possible mode-mismatch between the system mode and the accessible mode.Finally,an example is provided to demonstrate the effectiveness of the proposed control method.