〔Abstract〕 Objective To investigate the expression of circFAT1 in non-small cell lung cancer(NSCLC) tissues and the effect of silencing circFAT1 on the proliferation and invasiveness of NSCLC cell A549.Methods A total of107 patients with NSCLC who underwent surgical resection were selected. Real-time fluorescent quantitative PCR(RT-qPCR) was used to detect the expressions of circFAT1 in NSCLC and adjacent tissues. A549 cells were cultured and transfected with siRNA-circFAT1(si-circFAT1 group) and irrelevant sequences(si-control group),respectively,and in addition,the untransfected cells were set as the blank group. RT-qPCR was used to detect the expression of circFAT1 in cells,CCK-8 was used to detect cell proliferation,and Transwell chamber was used to detect cell migration and invasion.Results The relative expression level of circFAT1 in NSCLC tissues was higher than that in the adjacent tissues[(2. 47 ± 0. 27)vs(1. 02 ± 0. 15),t= 48. 959,P<0. 001]. Compared with TNM stagesⅠ-Ⅱ,moderately well differentiated and no lymph node metastasis,the relative expression levels of circFAT1 in NSCLC tissues with TNM stages Ⅲ-Ⅳ,poorly differentiated and lymph node metastasis increased(P<0. 05).Compared with the si-control group and the blank group,the relative expression level of circFAT1 in the cells of the si-circFAT1 group was significantly reduced(P<0. 05),and the numbers of migrating cells and invading cells were reduced(P<0. 05).Conclusion The relative expression level of circFAT1 in NSCLC tissues increased. Silencing circFAT1 can inhibit the proliferation,migration and invasion of A549 cells.