This research indicates that gas reservoirs in Jingbian Gasfield, Ordos, are characteristic of: (1) Gas is supplied by mixed gas sources from two directions; (2) Reservoir space are dominated by anhydrite-dissolved and dolomitized pores and subordinated by fractures; (3) Stratigraphic and lithogic traps are common and paleostuctures control the direction of hydrocarbon migration and emplacement; (4) Fluids in gas reservoirs are of heterogencity and negative pressure feature; (5) Formation water are compartmentally preserved without water beds. The mechanism resulting in these characteristics are discussed. The main geological factors leading to gas accumulation are owing to four "fitting match" conditions: (1) The match of enclosed sea with wide flats brings up good source-reservoir facies belt; (2) The match of erosion ridges with erosion grooves builds up layered dissolved currents; (3) The match of cutting with filling, and dissolution with filling, forms stratigraphic traps and lithologic traps; (4) The match of pore space with fissures nets gets to both gas reserves and output.