Osteoarthritis is a heterogeneous disease with complex etiology. However, there is no effective treatment strategy at present. The purpose of this study is to explore the miRNA-mRNA regulatory network and molecular mechanism that regulate the progression of osteoarthritis. In this article, we downloaded dataset (GSE55457, GSE82107, GSE143514 and GSE55235) from Gene Expression Omnibus (GEO) to screen differentially expressed mRNAs in osteoarthritis. Then, through weighted gene co-expression network analysis (WGCNA), functional enrichment, protein-protein interaction networks (PPI), miRNA-mRNA co-expression network, ROC curve, immune in ltration analysis and qPCR, the mRNA PLCD3, which was highly expressed in osteoarthritis and had clinical predictive value, was screened. Whereafter, we found that PLCD3 directly targets miR-34a-5p through DIANA and dual luciferase experiment. And the expression of PLCD3 and miR-34a-5p were negatively correlated. In addition, CCK-8 and wound healing showed that miR-34a-5p mimic inhibited hFLS-OA cell proliferation and promoted hFLS-OA cell migration.PLCD3 overexpression showed an opposite trend. Western further found that overexpression of miR-34a-5p reduced the protein expression levels of p-PI3K and p-AKT, while overexpression of PLCD3 also showed the opposite trend. Besides, combined with the effect of PI3K/AKT pathway inhibitor BIO(IC50 = 5.95 µM), the results showed that overexpression of miR-34a-5p increased the inhibitory effect of BIO on p-PI3K and p-AKT protein expression, while overexpression of PLCD3 signi cantly reversed the inhibitory effect. In all, the miR-34a-5p/PLCD3 axis may mediate the PI3K/AKT pathway in regulating cartilage homeostasis in synovial osteoarthritis. These data indicate that miR-34a-5p/PLCD3 may be a new prognostic factor in the pathology of synovial osteoarthritis.