A large amount of injected fracturing fluid is retained in tight reservoirs, leading to low flowback efficiency (less than 30%). It may be related to low fluid movability in tight reservoirs, which is influenced by the complex pore structure and mineral composition. However, effects of microstructure and rock mineralogy on movable fluid saturation in tight reservoirs have not been studied clearly. The tight sandstone cores from the Ordos Basin, China, are analyzed by conducting a series of experiments, including routine petrophysical measurements and X-ray diffraction, scanning electronic microscopy, and nuclear magnetic resonance (NMR) experiments. The quantitative analysis of the pore structure is carried out based on the fractal theory. The results show that NMR T-2 distribution is divided into four types. For the T-2 spectrum (0 < beta < 1) with a low left peak and a high right peak, the movable fluid saturation is 60.7% on average. Quartz has a positive correlation with movable fluid saturation, and clay minerals have a negative correlation with movable fluid saturation. It is caused by the high wettability of quartz and the strong cementation of clay minerals. Fractal dimension D-mov has a negative correlation with movable fluid saturation. The complex structure and irregular shape of tight sandstone reduce the movable fluid saturation. Movable fluid mainly comes from macropores whose relaxation time is greater than 10 ms. In addition, the movable fluid porosity of the cores has obvious differences, especially in the macropores. Several studies have shown that the microscopic pore structure and mineral composition of tight sandstone are the key factors that determine the content of movable fluid in the tight reservoir.