It is not easy to distinguish the effective and the invalid reservoir for tight sandstone reservoirs with low porosity and permeability. To develop tight sandstone reservoir economically and effectively, the effective thickness should be reconsidered. To study the characteristics of tight reservoirs with poor physical properties, we took reservoirs in the Funing Formation and Daiyi Member in Subei basin as an example. The relationship of four properties including lithology, physical property, oil-bearing property and electrical property was analyzed based on core analysis, formation testing, mercury injection, logs, etc. The lower limits of physical properties and electrical properties were studied using 5 methods, such as nuclear magnetic resonance, empirical statistics, minimum flow pore throat radius, etc. The results from different method agree with each other. Using the established lower limit standard, the effective thickness of five wells in the study area has been analyzed. The absolute error of logging interpreted effective thickness is -0.15 m by comparing with that defined by oil core. The accuracy of layer division is 100%. The proposed standard is in good agreement with the actual data and the operation is simple.