To discover the function of CONSTANS-LIKE 7 (COL7) in regulating plant flowering, we used qPCR, GUS staining, et al, to study the light and circadian regulating the expression of COL7, and COL7 regulating Arabidopsis flowering time. The results showed that COL7 was regulated by light and circadian, and the overexpressing COL7 transgenic lines inhibited Arabidopsis flowering time under long-day (LD) condition through down-regulating CONSTANS (CO) and FLOWERING LOCUS T (FT), and the col7 mutant had no obvious flowering phenotype under LD or SD conditions. So COL7 may have redundant functions with other CONSTANS-LIKEs (COLs) in controlling the flowering time of Arabidopsis.