Reduplication in Acehnese serves many functions such as plurality, reciprocity, emphasis, continuity, and repetitions. This word formation process has been previously analyzed in terms of morphology and traditional phonology. The present study was aimed at discovering constraint ordering of the reduplication to find out the rules which govern each pattern of reduplication in the language. The study employed Correspondence Theory under the umbrella of Optimality Theory, focusing on full and partial reduplication, leaving out rhyming reduplication due to framework limitation. The results show that all patterns of reduplication in Acehnese follow normal application where well-formedness proceeds faithfulness (MAX-IO) and precedes reduplicative identity (MAX-BR). The well-formedness for full reduplication only includes constraint of complex nucleus, where a final diphthong in the base changes to a monophthong in the reduplicant. For partial reduplication, constraint for well-formedness is that the syllable should be open, preceded by reduplicant size of no more than one syllable and alignment (either left for reduplicating prefix or right for reduplicating suffix). The well-formedness is proceeded by no insertion (DEP-BR). This study indicates the need to establish ranking of constraints which govern the phonology of Acehnese outside the context of reduplication, which is suggestion for future studies.