The invention provides a mercuric 
chloride low-mercury catalyst and a preparation method thereof. The catalyst adopts 
active carbon as a carrier to adsorb mercuric 
chloride, and the formula of the catalyst comprises 8.0 to 10.0 percent of mercuric 
chloride, 8 to 13 percent of 
rare earth chloride assistant A, 5 to 25 percent of 
alkaline earth metal chloride assistant B, 10 to 20 percent of assistant C, and the balance of 
active carbon. The preparation method comprises the following steps: firstly, soaking the 
active carbon in 
hydrochloric acid solution at low temperature for standby; simultaneously dissolving the mercuric chloride, the assistant A, the assistant B and the assistant C together, and soaking the active 
carton in the solution; performing low-temperature pre-
drying on an 
intermediate product; continuously 
drying the catalyst; and finally pumping a product at vacuum into a storage 
silo, packaging and leaving factory. The catalyst can reduce 
resource consumption and the pressure of treating 
mercury pollution; simultaneously the production cost is reduced, the poisoning resistance, reduction resistance and loss resistance are greatly improved, the catalytic performance of the catalyst is fully guaranteed, the using time can be prolonged and the using consumption can be reduced; and the catalyst is suitable for 
polyvinyl chloride manufacturers.