Heating characteristics of two types of used mercury-containing catalysts with different mercury content in microwave field were studied. Spent mercury catalysts were proved to be good microwave receptors. Heating curves were analyzed using heat transfer equation. With microwave heating, the sample temperature increased linearly, then increased gradually with considering heat loss, and finally reached an equilibrium value. Effects of material mass, microwave input power and particle size on heating behaviors were investigated. A proper material mass fitted with microwave power can lead to higher average heating rate and equilibrium temperature. Sample temperature increased with increasing input power at a constant material mass. Average heating rate was linearly related to input power. A good linear fitting relation between equilibrium temperature and input power was observed especially for catalyst support activated carbon and used low-level mercury catalysts.