Lower Ordovician Majiagou 51+2 gas reservoir is divided into 111 bed units in which include 69 independent and 42 compound ones. These bed units commonly are 10～50 km2 in extent of area, and the well number of a single bed unit is generally less than 6 wells. Comprehensive recognition of the reservoir bed units are founded on three key aspects, i.e. the identification of paleo-ravines, the research of compact belt and the analysis of combining dynamic and static data. The reservoir bed units are not only under the control of the favorable diagenetic belt that enclosed by dense rocks, but also under the control of different orders of paleo-ravines. Several reservoir bed units commonly coexist between two 1st-order paleo-ravines while the margins of these units are cut by 2nd-order and 3rd-order paleo-ravines.