Abstract: The dual-porosity tight sandstone reservoir has the characteristics of small pore throat and developed fractures,and the fluid occurrence status is different from that of the conventional reservoirs.The dynamic fluid parameter is an important parameter to evaluate the development potential of this kind of reservoirs.By using the nuclear magnetic resonance experiment,combining with the constant speed mercury injection,the movable fluid characteristics and main influencing factors of dualporosity tight sandstone reservoir of Chang 8 formation of Jinghe oilfield in south of Ordos basin were studied.The results show there are 5 typical T2 spectral curves in Chang 8 formation of Jinghe oilfield,the mean saturation of the movable fluid in reservoir is 44.8,the mean porosity of the movable fluid is 2.9%,the pore radius is 90~180μm,and the radius of the throat is 0.1~0.8μm,the horizontal seam density is 5.01~64.8/m,and the average is 21.1/m.Therefore,Chang 8 formation of Jinghe oilfield has the characteristics of low movable fluid percentage and low movable fluid porosity.The macroscopical properties of reservoir are strongly correlated with dynamic fluid parameters,and the better the property,the higher the fluid content.The main factors that control the fluid content of the dual-porosity tight sandstone reservoirs are the mainstream throat radius and the seam density.