The cathelicidins represent an important family of host defense peptides (HDPs) found exclusively in vertebrates, which serve as a critical effector in host immune response against microbial infections. To date, a large number of cathelicidins has been identified from diverse vertebrates, such as mammals, birds, reptiles, amphibians and fishes. Sixteen cathelicidins have been identified from snakes in the Elapidae, Viperidae, and Biodae families. However, no cathelicidin has been discovered from a snake of the Colubrinae family. In the present study, we report the identification and characterization of a novel cathelicidin, SA-CATH, from the Colubrinae family snake, Sinonatrix annularis. The cDNA sequence encoding SA-CATH precursor is 735 bp in length, and the mature peptide (SA-CATH) is composed of 30 amino acid residues. Sequence alignment result indicated that SA-CATH precursor possesses relatively high sequence similarity with the cathelicidins from Elapidae and Viperidae family snakes. Similar as the cathelicidins from Elapidae, Viperidae, and Biodae family snakes, SA-CATH mainly assumes an amphipathic alpha-helical conformation, and possesses potent antimicrobial, biofilm inhibitory and anti-inflammatory activities. The results in the present study imply that cathelicidins serve as a kind of conserved effectors with similar structures in the immune systems of Colubrinae, Boidae, Elapidae and Viperidae family snakes. The identification of SA-CATH provides novel clues for the understanding of function and evolution of snake immune systems. The potent antimicrobial, biofilm inhibitory, anti-inflammatory, and slight cytotoxic activities of SA-CATH imply that it is a potential drug candidate in novel antimicrobial agent development.