Abstract: In recent years, polymer flooding and polymer gel flooding field test have been carried out in SZ36-1 and LD10-1 oil field, with an obvious effect in increasing oil production and decreasing water production, finding an effective way to enhance oil recovery for offshore oil field. However, various complex environments and conditions in the reservoir may influence the crosslinking reaction. In this paper, experiment of the static gelling results of the crosslinking agent Cr³⁺ and polymer within core has been carried out through theoretical analysis and physical simulation experiment. The study results indicated that under the condition of static, cross-linking reaction between crosslinking agent Cr³⁺ and polymer molecules can occurs in the pores of core, and its gelling effect is influenced by core permeability and its type (whether including cement), core oil saturation, clay minerals type and content, and the influence degree of permeability is the largest. With the increase of core permeability, namely increasing in pore sizes, the gelling effect gets better in the core. With decreasing in oil saturation, the gelling effect gets better in the core. With increasing in clay content, the gelling effect gets worser in the core. Among the three core clay types, the effect of illite is biggest, followed by kaolinite, then followed by montmorillonite. The more loose of rock particles cemented, the better the gelling effect gets. These results have a guiding role for deep profile technology to improve development effect with weak gel in domestic and international oil fields.