Objective To investigate the expression of SAPCD2 in the lung adenocarcinoma cells, and to study the effect of SAPCD2 regulating Hippo signaling pathway on the proliferation, invasion, migration and apoptosis of the lung adenocarcinoma cells and its mechanism. Methods Quantitative real-time PCR (qRT-PCR) and Western blot were used to detect the expression levels of SAPCD2 mRNA and protein in four types of lung cancer cells (HCC827, H1650, SK-MES-1, A549) and human normal lung epithelial cells (BESA-2B), respectively. Then, lung cancer cells with relatively high levels of SAPCD2 expression were selected for subsequent experiments. The experiment cells were divided into a normal control group (NC group), a si-SAPCD2 group, and a pathway inhibitor group (si-SAPCD2+XMU-MP-1 group). Firstly, SAPCD2 mRNA was silenced using small interfering RNA (siRNA) technology, and then qRT-PCR was used to detect the expression of SAPCD2 in transfected lung cancer cells; using clone plate assay to detect the proliferation of lung cancer cells after silencing; using flow cytometry to detect the apoptosis of lung cancer cells after silencing; observe the number of lung cancer cells at different stages through cell cycle experiments; then Transwell experiment was used to analyze the effect of silencing SAPCD2 on the migration and invasion of lung cancer cell migration. Finally, Western blot was used to detect the expression of ki-67, Bcl-2, Caspase-3, NF2, P-MST1, P-LATS1, P-YAP, YAP, and TAZ proteins.Results SAPCD2 had the highest expression level in lung adenocarcinoma A549 cells (P<0.01). Silencing SAPCD2 significantly decreased the proliferation ability of A549 cells (P<0.01), inhibited their migration (P<0.05) and invasion (P<0.01), and promoted A549 cell apoptosis (P<0.01); more than half of the cells remained in the G0/G1 phase. Compared with the NC group, A549 cells showed a significant increase in G0/G1 phase cells (P<0.01), a significant decrease in G2/M and S phase cells (P<0.01), and a significant increase in the proportion of early apoptotic cells (P<0.01). Western blot results showed that silencing SAPCD2 down-regulated the expression of ki-67, Bcl-2, YAP, and TAZ proteins compared to the NC group (P<0.01), and up-regulated the expression of Caspase-3, NF2, P-MST1, P-LATS1, and P-YAP proteins (P<0.01). Conclusions The expression of SAPCD2 in lung adenocarcinoma A549 cells is significantly higher than that in normal lung epithelial cells (BESA-2B), which promotes the proliferation, migration and invasion of A549 cells and inhibits apoptosis. The mechanism may be related to the inhibition of Hippo signaling pathway.