Down-regulated miR-223-3p was found in rheumatoid arthritis. This study aimed to further explore the level and role of miR-223-3p in gout arthritis (GA). After monosodium urate (MSU)-induced GA rat and fibroblast-like synoviocytes (FLSs) models were established, the rat paw volume and gait score were documented and the FLSs were transfected with miR-223-3p mimic/inhibitor or NLR family pyrin domain containing 3 (NLRP3) over-expression plasmids. The MiR-223-3p target was found through bioinformatics and the dual-luciferase reporter. The rat joint pathological damage was observed by hematoxylin and eosin staining. The levels of interleukin (IL)-1β, tumor necrosis factor (TNF)-α and articular elastase in rats were detected by enzyme-linked immunosorbent assay (ELISA). The viability and pyroptosis of FLSs were detected by methyl thiazolyl tetrazolium (MTT) and flow cytometry. The expressions of miR-223-3p, NLRP3, cleaved caspase-1, IL-1β, apoptosis-associated speck-like protein (AS) and cleaved N-terminal gasdermin D (GSDMD) in FLSs or rat synovial tissues were detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), immunofluorescence, Western blot or immunohistochemistry analysis. MSU increased the paw volume, gait score, inflammation in synovial tissues and increased the levels of IL-1β, TNF-α and articular elastase in rats. MSU decreased the viability and increased the pyroptosis of FLSs, up-regulated the expression of NLRP3, ASC, cleaved caspase-1, cleaved N-terminal GSDM, and IL-1β, and down-regulated miR-223-3p expression in synovial tissues of rat joints and FLSs. MiR-223-3p mimic reversed the effect of MSU on lowering cell viability, increasing pyroptosis in FLSs, while miR-223-3p inhibitor further enhanced the effect of MSU on FLSs. NLRP3 was a target of miR-223-3p. Also, NLRP3 over-expression reversed the effects of miR-223-3p on MSU-induced FLSs. MiR-223-3p inhibited pyroptosis in MSU-induced rats and FLSs by targeting NLRP3.