Abstract: Objective To determine the H9C2 cell damage and NLRP3 inflammasome activation trigged by soluble uric acid (UA). Methods H9C2 cells were treated with UA. The cellular damage was examined after 12 h, 24 h and 48 h of treatment using MTS and lactic dehydrogenase (LDH). The apoptosis of H9C2 cells was analyzed by flow cytometry (FCM). NLRP3 inflammasome activation was reflected by the protein levels of NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC) and Caspase-1 detected by Western blot. The mitochondria and cytoplasm were separated and the release of cytochrome C was detected by Western blot to analyze the damage of mitochondria. The impacts of NAC, a ROS inhibitor, on the cell viability and NLRP3 inflammasome activation were analyzed. The expression of UCP2 was detected by Western blot and immunofluorescence (IF). Results Dose response and time dependent effects of UA on cellular damage and cell apoptosis was observed. UA up-regulated the expression of NLRP3 inflammasome-related molecules. UA damaged the mitochondria. NAC improved the cell viability and inhibited NLRP3 inflammasome activation. UA down-regulated the expression of UCP2. Conclusion Soluble UA can down-regulate the expression of UCP2, damage the mitochondria and activate NLRP3 inflammasome, resulting in cellular damage of H9C2 cells.