Abstract: MADS-box gene is a key transcription factor that plays crucial roles in plant development, especially controlling the formation and development of floral organs. We cloned the flower-specific gene from floral organs of Ananas comosus, named AcMADS1 (GeneBank accession no. KC257408), was cloned by homology-based cloning and RACE. The open reading frame of AcMADS1 was 726 bp, encoding 241 amino acids with molecular weight 27.5 kDa and isoelectric point 9.26. Sequence alignment and phylogenetic tree analysis indicated that the deduced protein AcMADS1 contained a conservative MADS-box and semi-conservative K domain and belonged to the AGL6 clade of the MADS-box family. Bioinformatics analysis demonstrated that AcMADS1 was an alkaline and hydrophilic protein; the secondary structure comprised an α-helix, a random coil and an extended strand; the protein core structure agreed with the transcription factors and the function of the common DNA combining domain MADS-box in its protein 3D model and was located in the nucleus as a transcription factor. Tissue-specific analysis showed that AcMADS1 was expressed in floral organs (pistils, petals and sepals) and flesh of pineapple, with nearly no transcription detected in vegetative organs (roots, stems and leaves) and stamens. Furthermore, the expession of AcMADS1 was higher at the early phase of floral development, then reduced at the late phase. AcMADS1 may have important roles in floral induction and floral development of pineapple.