AbstractSpent low‐level mercury catalyst (SLMC) from the polyvinyl chloride industry is a mercury‐containing hazardous waste. Thermal treatment technology was used to detoxify SLMC and recover mercury in this paper. Effects of flow rate of nitrogen, treatment temperature, and time on mercury removal efficiency were estimated 99.91% of total mercury was removed when SLMC was treated at 600°C for 30 min with 120 L/h of nitrogen. SLMC could be detoxified after being treated at 350°C for 120 min, 400°C for 60 min, or 450°C for 10 min based on the TCLP test. Migration rule of mercury during thermal treatment was analyzed by using improved sequential extraction procedure. Soluble and exchangeable mercury, and mercury combined with labile organics, were removed more easily than HgS and mercury combined with non‐labile organics. Removal process of total mercury followed a first‐order kinetic model. The experimental results may be useful for disposing of SLMC using thermal treatment in engineering practise.