Background:　Lung　cancer　is　the　leading　cause　of　cancer-related　death　in　the　world,　with　metastasis　as　the　main　reason　for　the　mortality.　CELF1　is　an　RNA-binding　protein　controlling　the　post-transcriptional　regulation　of　genes　related　to　cell　survival.　As　yet,　there　is　little　knowledge　of　CELF1　expression　and　biological　function　in　lung　cancer.　This　study　investigated　the　expression　levels　of　CELF1　in　lung　cancer　tissues　and　the　biological　function　of　CELF1　in　lung　cancer　cells.　Methods:　CELF1　mRNA　expression　was　determined　in　lung　cancer　and　normal　tissues,　and　the　relationship　between　the　expression　level　of　CELF1　and　clinicopathological　parameters　was　evaluated.　The　biological　function　of　CELF1　in　A549　and　H1299　lung　cancer　cell　lines　growth　was　examined.　Results:　The　expression　of　CELF1　was　higher　in　human　lung　cancer　tissues　compared　with　the　normal　lung　tissue.　Lentiviral-mediated　transfection　of　CELF1　siRNA　effectively　silenced　the　expression　of　CELF1　in　both　A549　and　H1299　cells.　Moreover,　CELF1　knockdown　markedly　reduced　the　survival　rate　of　lung　cancer　cells.　Colony　formation　assays　revealed　a　reduction　in　the　number　and　size　of　lung　cancer　cell　colonies　from　CELF1　knockdown.　Conclusion:　These　results　indicated　that　CELF1　may　have　significant　roles　in　the　progression　of　lung　cancer,　and　suggested　that　siRNA　mediated　silencing　of　CELF1　could　be　an　effective　tool　in　lung　cancer　treatment.