OBJECTIVE：To discuss the mechanism of synovitis of knee osteoarthritis （KOA）relieved by “Sanse powder ” volatile oil based on the activation of Nod-like receptor family 3（NLRP3）inflammasome. METHODS ：“Sanse powder ”volatile oil was extracted by distillation- condensation process and the components of it were analyzed by GC-MS. Fibroblast-like synovial cells（FLS）were extracted from the knee joint of male SD rats. The effects of 10，25，50，100，250，500，1 000 μg/mL“Sanse powder”volatile oil on the viability of FLS were examined by CCK-8 assay. KOA inflammatory cell model was induced by lipopolysaccharide for 12 h. The effects of 10，250 μg/mL“Sanse powder ”volatile oil on the protein and mRNA expression of NLRP3，caspase-1 and apoptosis-associated speck-like protein （ASC）were detected. The levels of IL- 1β and IL-18 in supernatants of FLS were determined . RESULTS ：Totally 0.51-0.61 g volatile oil with yellow clear and unique aromatic odor were extracted from“Sanse powder ”，and the extraction rate was 0.33％-0.41％（n＝9）. A total of 41 chemical components were isolated ，and 30 of them were identified and their peak area accounted for 90.073 6％ of the total peak area. The components with high relative content were gingerol flavonoids （17.573 9％），δ-junionene（15.434 5％），gingerol（11.509 5％），etc. When the concentration of volatile oil was 10-250 μg/mL，there was no significant effect on survival rate of FLS （P＞0.05）. Compared with blank group ，the relative protein and mRNA expression of NLRP 3，caspase-1 and ASC and the levels of IL- 1β and IL-18 in supernatant were significantly increased in model group （P＜0.05）. Compared with model group ，relative expression or levels of above indexes were all decreased significantly in FLS and supernatant of “Sanse powder ”volatile oil 10 and 250 μg/mL groups（P＜0.05）. CONCLUSIONS：“Sanse powder ”volatile oil can inhibit NLRP 3 inflammasome activation in FLS and reduce the downstream inflammatory cascade response ，thus exerting its efficacy in ameliorating synovial inflammation of KOA.