Abstract: Based on the analytical data of core,scanning electron microscopy,casting thin sections of Chang-6 reservoir in Wu Cangbao area of Ordos basin,the analysis results show that the content of feldspar and quartz of Chang-6 reservoirs sandstone is high,and the rock types are mainly of fine-grained lithic feldspathic sandstone,and the compositional maturity and textural maturity are lower.According to morphology of capillary pressure curve and pore structure characteristics parameters,the capillary pressure curve of the study area can be divided into three categories,class I,class II and classⅢ.The rock type of Chang-6 reservoir in Wu Cangbao area belongs to fine grained lithic arkose,the sandstone compositional maturity and structural maturity are lower,the reservoirs are mainly of intergranular pore and intragranular pore,with the average porosity of 9.17% and the average permeability of 1.21x10~(-3)μm~2,belonging to extra low porosity- extra low permeability reservoir,and the pore is given priority to with primary pore.