Abstract: Saline aquifer has the most sequestration potential among all the sites that can implement CO2geological sequestration. Structual stratigraphic sequestration is the basic mechanism which can affect CO2storage capacity in a saline aquifer. In this paper, an experimental method is used to measure the irreducible water saturation to a rock sample, a key parameter that affects structual stratigraphic storage capacity. The rock sample is taken from the Ordovician reef limestone in the Tarim Basin, which is widely considered to be rich in oil and gas, Firstly, effective porosity and permeability coefficient of the sample are measured with saturated weighing and permeating experiment, and are 00283, 556×10-9 m/s, respectively. Irreducible water saturation is measured through supercritical CO2flooding core saturated water under simulating strata temperature of 40℃ and strata pressure of 8 MPa, and the result is 0451 Meanwhile, the changes in pressure and flux with time are observed during the core flooding experiment through supercritical CO2.