On the basis of the outcrop profile measurement and sample collection，through casting sheet identification，cathodoluminescence analysis，X-ray diffraction analysis，scanning electron microscopy analysis，geochemical analysis of total organic carbon content and vitrinite reflectance，the characteristics of shale reservoirs in the Ordovician Wufeng FormationSilurian Longmaxi Formation（Wufeng-Longmaxi Formation）were discussed combined with the regional geological background and previous research results in Yanzikou area，northwestern Guizhou with the following results obtained：①The rock types of Wufeng-Longmaxi Formation are dominated by silty shale，dolomitic/calcareous shale，and argillaceous siltstone deposited in shallow water-deep water shelf environment，and the black carbonaceous/siliceous shale in Wufeng Formation and lower Longmaxi Formation are potential source rocks. ②The mineral composition mainly includes clay minerals （22%-51%），quartz（21%-41%），and carbonate minerals（10%-35%），with a small amount of pyrite and gypsum，of which clay minerals mainly include illite/smectite mixed layer and illite. Generally，it has a large proportion of brittle miner? als（average 59.4%），strong heterogeneity，and great vertical variation. ③Reservoir space consists mainly of interlayer cracks，dissolution pores，and bedding fractures.Carbonate and feldspar dissolution phenomena are especially obvious，but organic pores are underdeveloped. ④The effective thickness of source rocks with a total organic carbon content of more than 1% in the Wufeng-Longmaxi Formation is about 20 m. ⑤The equivalent vitrinite reflectance of the Wufeng-Longmaxi Formation is around 2.5%，showing its high degree of thermal evolution. It is in the stage of overmature dry gas and is still capable of hydrocarbon generation.