Abstract: Objective: To explore the expression of cyclin dependent kinase-like 1(CDKL1) in lung adenocarcinoma(LUAD) and its effect on the proliferation, invasion and migration of LUAD cells. Methods: TCGA database was used to analyze the difference of CDKL1 gene expression between LUAD and normal lung tissues. Kaplan-Meier Plotter database was used to analyze the relationship between CDKL1 gene expression level and prognosis of LIAD patients. The mRNA and protein expression levels of CDKL1 in 78 LUAD tissues and adjacent tissues were detected by real-time fluorescence quantitative polymerase chain reaction(RT-qPCR) and western blotting, and the relationship between the expression level of CDKL1 and clinicopathological features of LUAD patients was analyzed. LUAD cell line NCI-H1975 was cultured in vitro. The CDKL1 overexpression plasmid and its empty vector plasmid were transfected into NCI-H1975 cells, and divided into blank group, Vector group and CDKL1 overexpression(oe-CDKL1) group. Cell proliferation activity was detected by cell counting kit-8(CCK-8) and BrdU methods; cell apoptosis was detected by flow cytometry and the changes of cell invasion and migration ability were detected by Transwell. The expression level of apoptotic protein Cleaved-caspase-3 was detected by western blotting. Results: Compared to normal lung tissues, the expression of CDKL1 was lowly expressed in human LUAD tumor tissues(P＜0.05) and its low expression was significantly associated with various pathological parameters such as tumor size, TNM stage, differentiation degree, lymph node metastasis, and poor prognosis of LUAD patients(P＜0.05). Compared with the blank group and Vector group, CDKL1 gene of NCI-H1975 cells in the oe-CDKL1 group was significantly up-regulated(P＜0.05), cell proliferation activity was significantly decreased(P＜0.05), cell invasion and migration abilities were significantly decreased(P＜0.05), cell apoptosis was increased(P＜0.05), and Cleaved caspase-3 protein expression level was significantly increased(P＜0.05). Conclusion: The CDKL1 is lowly expressed in LUAD tumor tissues. Its overexpression of CDKL1 can inhibit the proliferation, invasion and migration of LUAD cells, and induce apoptosis.