The Dongshengmiao deposit is a superlarge lead zinc polymetallic deposit occurring in the Langshan-Zhaertaishan metallogenic belt of Inner Mongolia, and the main ore-bearing rock is the second Formation of Langshan Group. In this paper, the authors combined the study of multiple suites of core samples which cover the main ore-bearing rock series with the recent study of hydrothermal deposits abroad, and arrived at some new understanding of the major orebody of the Dongshengmiao deposit. The rock and ore in different lithologic members have different fabric characteristics: in the middle of the fourth lithologic member, siderite ores show fine mosaic texture and massive structure, with obvious characteristics of chemical sedimentation; at the bottom of the fourth lithologic member, sphalerite ores of the No. 2 orebody exhibit hypautomorphic-allotriomorphic crystalline granular texture or dissolution texture, and mostly show massive, banding or brecciated structure, with obvious filling-metasomatic phenomenon; stockwork mineralization is generally existent in the third lithologic member which is sericite-grapholite based, with very common later hydrothermal filling phenomenon. In addition, geochemical study of the rock and ore indicates that siderite ore shares similar trace element enrichment and REE distribution pattern to sphalerite ore, so they may have had the same provenance. However, sericite-grapholite in the third lithologic member has different trace element enrichment features and REE distribution curves,probably resulting from multi-stage hydrothermal activity. It is worth mentioning that we can find dolomite-marble fragment breccia which belongs to upside wall rock and they are different from sericite-grapholite fragment breccia. The dolomite-marble fragment breccias resulted probably from replacement. Comprehensive analysis shows that stockwork mineralization in the third lithologic member was caused by later hydrothermal filling, while the No.2 orebody at the bottom of the fourth lithologic member might have resulted from ore-bearing hydrothermal selective replacement of carbonate strata, and siderite orebody's mineralization might be attributed to the migration of the iron-rich hydrothermal solution to the bottom of ocean and the subsequent precipitation. Ore-bearing hydrothermal replacement played a key role in the ore-forming progress of the major orebody in the Dongshengmiao deposit. The result achieved by the authors has deepened the understanding of the SEDEX deposit.