Abstract: Provided is a leaching-seepage process of sodium sulfate in a thenardite tailings stack. The process includes the following steps: step 1, providing a mud reserve pit next to the thenardite tailings stack, and ditching a drainage ditch next to a bottom of the thenardite tailings stack; step 2, ditching a leaching pit on the thenardite tailings stack, injecting water, and letting the water stand to leach thenardite tailings; step 3, leaching the thenardite tailings with the water, so that a percolating fluid gradually flows out from the bottom of the thenardite tailings stack; step 4, flushing the bottom of the thenardite tailings stack with a spray gun, to mix the percolating fluid with mud to flow into the drainage ditch; and step 5, settling naturally in the mud reserve pit, and extracting a supernatant from the mud reserve pit by a water pump to obtain refined Glauber's salt water.