Abstract: In order to obtain the effectively quantitative analysis on micro-pore structure and physical property of Chang Ⅱ sandstone reservoir of Liuluowan block in Xiasiwan oilfield , the rate-controlled mercury penetration technique based on conventional test of reservoir has been used to analyze the micro-pore structure and evaluate its effect on the reservoir physical property.This study indicates that the average throat radius is small in low and extra-low permeability reservoir.Although the pore throat distribution ranges of core samples with the same porosity are similar , the ratios of pore radius to pore throat radius vary significantly.The characteristics of throat structure dominate the heterogeneity degree of sand reservoir.A good correlation has been found between reservoir physical property and the parameters of micro-pore structure.The results also show that the effect of distribution characteristics of throat structure on reservoir permeability is significant and increasing the proportion of big throat and improving the connectivity between pores can enhance the development effect of low and ultra-low permeability reservoir.