The CO family gene regulates flowering time by integrating circadian rhythms, light signals, and meristem-related genes through the photoperiod pathway, and plays a crucial role in the process of plant flower formation. In this study, a CO family gene cloned from Chrysanthemum lavandulifolium by RT-PCR method, was named ClCOL16 (GenBank accession number: AOA52174.1), and ectopic expressed in Arabidopsis thaliana by Agrobacterium-mediated method. The results showed: (1) ClCOL16 gene ORF was 1278 bp and encoding a protein of 425 amino acids Structural analysis showed ClCOL16 protein contains a B-box and a CCT conserved domain, which is a typical characteristic of CO family Group III. (2) NCBI blast analysis showed that ClCOL16 protein had the highest identity with COL16 (GenBank accession number: GEZ38716.1) from Tanacetum cinerariifolium, up to 94.38%, which further proved that it belongs to the CO family Group III. (3) Expression analysis showed that ClCOL16 gene was constitutive expression in C. lavandulifolium, and the highest exspression was in leaves；ClCOL16 gene was regulated by circadian clock, under short-day condition its expression showing obvious circadian rhythm. (4) Ectopic expression showed that the flowering time of ClCOL16 transgenic Arabidopsis thaliana was significantly earlier than that of wild type plant, indicated that ClCOL16 gene may be involved in the photoperiod flowering pathway in chrysanthemum. This study laid the foundation for further study on mechanism of chrysanthemum flowering time regulation.