Actin-depolymerizing factor (ADF) plays an important role in remodeling the actin cytoskeleton which contributes much to the invasion of host cells by the apicomplexan parasite. The gene encoding for Eimeria tenella ADF with one intron was cloned and identified by the E. tenella genome raw sequence data ( http://www.sanger.ac.uk/projects/E.tenella/ ). The deduced polypeptide sequence was only composed of 118 amino acids (13.14 kDa) without signal peptide and nuclear localization sequence. The amino acid sequence was most similar to the ADF of Toxoplasma gondii, 69.1%. Compared the putative three-dimensional structures between E. tenella and yeast, the actin filament binding sites on the segment from the alpha4-helices to the C-terminal were mostly missed in E. tenella. Real-time RT-PCR and dot blot both revealed that ADF expression was relatively stronger in the sporozoites and merozoites than in sporulated and unsporulated oocysts in both mRNA and protein levels. Northern blot analysis suggested that there was only one form of ADF transcripts in all different life stages of E. tenella. Actin-binding experiment showed that the recombinant fusion ADF protein could bind with actin, which indicated that ADF probably plays an important role in the invasion host of E. tenella.