The NLRP3 inflammasome is unique among pattern recognition receptors in using changes in cellular physiology as a mechanism for sensing host danger. To dissect the physiological network controlling inflammasome activation, we screened for small-molecule activators and suppressors of IL-1β release in macrophages. Here we identified niclosamide, a mitochondrial uncoupler, as an activator of NLRP3 inflammasome. We find that niclosamide inhibits mitochondria and induces intracellular acidification, both of which are necessary for inflammasome activation. Intracellular acidification, by inhibiting glycolysis, works together with mitochondrial inhibition to induce intracellular ATP loss, which compromises intracellular potassium maintenance, a key event to NLRP3 inflammasome activation. A modest decline in intracellular ATP or pH within an optimal range induces maximum IL-1β release while their excessive decline suppresses IL-1β release. Our work illustrates how energy metabolism converges upon intracellular potassium to activate NLRP3 inflammasome and highlights a biphasic relationship between cellular physiology and IL-1β release.