Abstract: J2Ⅱ (ZhujiangⅡ)oil series is the objective pay zone in Weizhou XX oilfield. The core and logging data show that there are some inter-layers developed in the J2Ⅱ oil series.It is unable to further study the effect of the inter-layer on the rising velocity of water-cutting due to the limitation of relevant data and the uncertainty of the distribution range of inter-layer. Based on the core and well logging data,the authors conducted a fine study on the inter-layer through dividing the inter-layer into argillaceous inter-layer and calcareous inter-layer, determining the identification method and calculation model of inter-layer, and establishing the criteria of inter-layer classification by permeability.It can be divided into three levels by three grades of permeability,namely medium-high permeability, low permeability and extra-low permeability. The fine depiction of inter-layers in J2Ⅱ oil series provided key information for re-establishing the fine geological model, and also laid a foundation for the subsequent reservoir numerical simulation study of water-cutting rising.