Abstract: The Houziping mercury deposit, occurring in the micro-fine grained laminated dolomite in upper Aoxi formation, Middle Cambrian, is located at the axis of a gentle and broad half-anticline, which trends 120° and extends more than 1100 m deep, the deepest among the deposits in the Hunan-Guizhou mercury ore belt. Particularly, the cinnabar crystal occurred in the deposit is greatly valued for its attractive colors and beautiful forms. Study shows that the mercury deposit is formed during the wet gas stage in oil-gas reservoir evolution, spatially related to paleo-reservoir. Both of the deposits are from the same source and reserve, with similar ore-forming mechanism.