in the buried Jingbian Buried Platform and its periphery area of Ordos Basin, the sedimentary environment of Middle Ordovician Majiagou 51-4 Sub-member reservoir is generally the inner shelf basin-marginal flat facies. The Majiagou 51-4 reservoir consists of silt-sized crystalline dolostone. Difference of lithology is the basic factor that controls heterogeneity of the reservoir. Silt-sized crystalline dolostone with anhydrite-nodules and/or columnar crystallines plays a predominant role in controlling heterogeneity in this area. Other controlling factors are geologic background, palaeokarst diagenesis, tectonic fissures, fault distribution，etc. In addition, palaeogeomorphology, effective thickness of reservoir and development of non-reservior are also effective. The main gas-producing zone is in Jingbian Platform but the reservoir did not well-developed or along the west part of the platform where strata are severely eroded and the east part rock is heavily dissolved.