Shale oil and gas have been drilled in the Chang 7 lacustrine shale in Zhangjiawan area of Ordos Basin.The pore type,pore size and distribution of shale have important effects on the physical property,reservoir permeability,the occurrence state and content of shale oil and gas.The Chang 7 shale reservoir geochemical characteristics and pore types,pore size distribution and influencing factors were analyzed by using argon ion polishing and field emission scanning electron microscopy (SEM) analysis,the low pressure CO₂,N₂ adsorption,XRD and other test methods in this paper.Results show that the thickness of the shale ranges from 30 to 110m.The average TOC is 4.97%,the average content of soluble hydrocarbon is about 4.54g/g,the average content of chloroform bitumen “A” is 0.80%,and RO is between 0.6% and 1.1%.Shale pore types include residual intergranular pores,intergranular dissolution pore,intragranular dissolution pore,intercrystalline pores of pyrite and clay minerals,organic pores.About 61 percent of the organic pores are micro-pores and meso-pores,with diameter less than 50 nm.The pores of intergranular pores and intraplasmic dissolution pores are relatively large.The diameters of the pores of clay minerals are relatively small.The porosity of Chang 7 shale is between 0.8% and 6.5%,with an average of 3.2%.The pore diameter is between 0.8nm and 10μm,and it has the characteristics of multi-peak distribution.The pore diameter distribution curves of samples with different lithology and rock composition are quite different.The more developed the siltstone and fine sandstone laminar in shale,the larger the particle size of detritus,the higher the content of quartz and feldspar,the lower the content of clay minerals,the more developed the middle and large pores,and the greater the porosity.The higher the total organic carbon content and organic matter evolution,the more developed the organic pore.