【Objective】 To explore the effects of long non-coding RNA maternally expressed gene 3 (lncRNA MEG3) on the invasion and migration of prostate cancer cells (PC3 cells) by regulating microRNA-181b-5p (miR-181b-5p)/tissue inhibitor of metalloproteinase 3 (TIMP3). 【Methods】 The prostate cancer tissues and adjacent tissues were collected from 20 prostate cancer patients treated in our hospital during Dec.2020 and Dec.2021. The expressions of MEG3 and miR-181b-5p in tissues were detected with quantitative real-time PCR (qRT-PCR). P3 cells were randomly divided into control group (untreated), pcDNA3.1-NC (transfected with pcDNA3.1-NC), pcDNA3.1-MEG3 group (transfected with pcDNA3.1-MEG), pcDNA3.1-MEG3+miR-NC group (pcDNA3.1-MEG3 co-transfected with miR-NC), pcDNA3.1-MEG3+miR-181b-5p mimic group (pcDNA3.1-MEG3 co-transfected with miR-181b-5p mimic). The expressions of MEG3 and miR-181b-5p in PC3 cells were detected with qRT-PCR. The cell viability, invasion and migration ability were determined with MTT assay, Transwell assay and scratch assay. The protein expressions of TIMP3, matrix metalloproteinase (MMP)9 and MMP2 in PC3 cells were detected with Western blot. The targeting relationship of MEG3, miR-181b-5p and TIMP3 was analyzed with dual luciferase assay. 【Results】 The expressions of MEG3 in prostate cancer tissues ( 0.37±0.05 vs. 1.00±0.04) and cells (0.31±0.06 vs. 1.00±0.01) were significantly decreased (P<0.05). Compared with the control group, the pcDNA3.1-MEG3 group had significantly decreased expression of miR-181b-5p (0.26±0.04 vs.1.00±0.02 ), cell survival rate (53.60±5.22 vs.100.00±0.00), number of invasive cells (62.33±9.85 vs.162.34±21.30), cell migration rate (32.85±3.80 vs.75.22±5.96), expressions of MMP9 (0.61±0.08 vs.1.62±0.23) and MMP2 (0.73±0.10 vs.1.20±0.16), but significantly higher expressions of MEG3 (2.31±0.36 vs. 1.00±0.01) and TIMP3 (1.32±0.24 vs. 0.53±0.08) (P<0.05). Overexpression of miR-181b-5p reversed the above changes (P<0.05). MiR-181b-5p had a targeting relationship with MEG3 and TIMP3. 【Conclusion】 Overexpression of lncRNA MEG3 can inhibit miR-181b-5p to promote the expression of TIMP3, thereby inhibiting invasion and migration of PC3 cells.