Abstract:MADS-box family proteins are important transcription factors associated with the regulation of growth and development, especially in floral development of higher plants. HAM23-like, a new member of the MADS-box genes, was cloned from Helianthus annuus. The bioinformatic results revealed that HAM23-like gene had an open reading frame of 831 bp, encoding a protein with 276 amino acid; the protein possessed a relative molecular weight of 30.52 kD and a theoretical isoelectric point of 9.42. The analysis of phylogenetic tree showed that HAM23-like was closely homologous to the AGL18 gene of Arabidopsis thaliana. Moreover, the qRT-PCR results indicated that the HAM 23-like gene were highly expressed in flower and mature fruit in tissue expression pattern, and in different floral organ of flowering day, the expression of HAM23-like reached the highest level in stamen. In addition, the expression of the HAM23-like gene was gradually raised during the floral development, and reached the highest expression on 5 days after flower blooming. These results implied that HAM23-like gene would be involved in the later stage of floral organs development and the earlier stage of achene development in H. annuus. The results of this study could provide some preliminary data and theoretical basis for further study, especially, it will help to explore the regulatory role of HAM23-like in floral development and achene formation in H. annuus.