Abstract: In order to explore the differential characteristics of fluid occurrence in tight sandstone reservoirs, the Chang 6 and Chang 8 reservoirs in the Triassic Yanchang Formation in HQ and HS areas of the Ordos Basin were employed as research objects, the movable and non-movable fluid saturation of reservoir rocks were quantitatively analyzed with features including permeability interval, area and target strata by using nuclear magnetic resonance (NMR) test and high-speed centrifugal experiments. Results showed that the total movable fluid saturation, as well as the main throat intervals of movable fluid were different in reservoirs with different permeability levels. For the high permeability, movable fluid was mainly controlled by larger throat, while for the low permeability, movable fluid was mainly controlled by smaller throat. Movable fluid saturation positively correlated to the throat radius in the smaller throat radius range (< critical throat radius), and negatively correlated to throat radius in the larger throat radius range (>critical throat radius). The higher the permeability, the larger the critical throat radius.