Abstract: This study sought to assess the therapeutic effect of celecoxib (CEL)-loaded polylactic acid-glycolic acid copolymer (PLGA) microspheres on rheumatoid arthritis in rats after intra-articular injection.The celecoxib-loaded microspheres (CEL-MS) were prepared by the O/W solvent volatilization method with PLGA as carrier.In order to investigate the therapeutic effect of CEL-MS on rheumatoid arthritis in rats after intra-articular injection, a rat model of adjuvant arthritis (AA) was constructed by complete Freund''s adjuvant, and the evaluation indicators of the therapeutic effect were rat paw swelling, arthritis index,spleen index and joint synovial histopathological examination. The results showed that the microspheres had a smooth spherical morphology with a particle size of (2.1 ± 0.3) μm and a drug loading efficiency of (20.8 ± 0.6)%.The results of the in vivo efficacy test showed that intra-articular injection of CEL-MS compared to the CEL suspension oral and the celecoxib suspension intra-articular injection in adjuvant arthritis rat model can significantly reduce joint swelling and arthritis index, thus effectively inhibiting synovial inflammation.The above results indicate that intra-articular injection of CEL-MS has a good therapeutic effect on rheumatoid arthritis in rats.