This study adopts cast thin section analysis, high-pressure mercury porosimetry, constant-speed mercury porosimetry, X-ray diffraction, NMR and seepage experiments to investigate the pore structure and its influence on precolation of the Chang 8 tight sandstone reservoir in the Zhouchang Area. The result shows that the reservoir space is dominated by intergranular pore and feldspar dissolved pore with a low average surface porosity. Throat type mainly develops flaky-curved lamellar and necking throat. The reservoir exhibites a low displacement pressure and the mercury injection saturation is high, but the mercury ejection is low because of poor pore-throat connectivity and clay minerals. The main factor affect percolation characteristics with tight sand reservoir is the pore structure features. Among the pore structure parameters, throat size, pore-to- throat ratios and connectivity between pores and throats are the key impacting percolation capacity. Research also indicates that the large throats is the more contribution to the reservoir percolation; Whereas, middle to small sized pore throat is relatively contributes more to reservoir quality.