Recently, fuzzy n-ary polygroups were introduced and analyzed by Davvaz, Corsini and Leoreanu-Fotea. Fuzzy n-ary polygroups are suitable generalizations of n-ary polygroups and a special case of fuzzy n-ary hypergroups. The aim of this paper is to introduce the notion of an interval-valued fuzzy n-ary subpolygroup of an n-ary subpolygroup and to extend the fuzzy n-ary subpolygroup to interval-valued (is an element of, is an element of boolean OR q)-fuzzy n-ary subpolygroup. We also consider the concept of implication-based interval-valued fuzzy n-ary sub-polygroup in an n-ary polygroup. in particular. the implication operators in ukasiewicz pound system of continuous-valued logic are discussed.