A Lower-Middle Ordovician Yingshan weathering-crust reservoir develops in Yubei area in Markit Slope, Tarim Basin. Affected on multi-stage faulting and paleo-karstification, it is difficult to identify karstification stages and fracture effectiveness. Based on observation and geochemical analysis of core samples and microscopic thin-slices, combined with logging and seismic interpretation, four assemblages of related reservoir rocks are recognized in Yingshan Formation and some correlations of porosity with permeability are diagramed for these rock assemblages. It is suggested that the reservoir property of Yingshan Formation is closely related to the early to middle Ordovician faulting and fracturing. The multi-stage faulting and the karstification experienced during Ⅰ and Ⅲ phases of Middle Caledonian movement effectively improved the reservoir property of limestone in the uppermost part of Yingshan Formation and the dolomitization improved the porosity of crystalline dolostone in the lowermost part of it.