Abstract: Taking Phalaenvpsis ’Big Chili’ as experiment material,cloning full length cDNA of Phalaenopsis APETALA1 gene by RACE and analysis of basic biological infamati.The results showed full-length cDNA of AP1 gene was 1 155 bp with a 752 bp open reading frame encoding a putative protein of 250 amino acids.It contained conservative functional domains such as MADS-box and K-box.The results of homology comparison showed that the MADS proein of Phalaenopsis ’Big Chili’ had high similarity with other plants,such as Dory butterfly,Cymbidium formosans,Oncidium,Dendrobium and Aristolochia,and the homology was more than 80%.Phylogenetic tree analysis showed that the AP1 gene of Phalaenopsis ’Big Chili’ had the closest relationship with the clustering of Dory butterfly.qRT-PCR showed that the mRNA of AP1 was widely expressed in all tissues tested（leaves,roots and pedicels）,but the expression level was different.There was no signficant difference of AP1 gene expression in leaves of different developmental stages of the same organ.The expression level of AP1 gene in roots decreased with the process of flower bud differentiation,the lowest level at the beginning flowering stage,and the highest at the full flowering stage;while the expression of AP1 gene in the scape increased with the flower bud differentiation,and the highest at the full flowering stage.Comparison of different organs in the same period,the expression of AP1 in pedicel was significantly higher than that in leaves and roots（P＜0.05）.Therefore,we speculate that AP1 gene plays an important role in the regulation of flower bud differentiation in Phalaenopsis.