Numerical simulation is one of critical techniques for the quantitative characterization on remaining gas, scheme optimization of reservoir adjustment, and production prediction. For tight sandstone gas reservoirs, however, their complex geological conditions and flow behaviors make the accurate description of remaining-oil distribution impossible by using conventional simulation techniques. Thus, for fine characterization of remaining gas in tight sandstone reservoirs, Taiyuan 2 gas reservoirs of Daniudi gasfield in Ordos Basin were taken as examples to explore the effect of flow behaviors on production. Moreover, coupling with reservoir engineering and laboratory experiments, the equivalent characterization on start-up pressure gradient, water-locking effect and stress sensitivity was conducted in numerical simulation according to seepage theories in tight sandstone reservoirs. Results show that (i) due to both formation-pressure drop and another fluid or gas invasion after reservoir development, there induced stress sensitivity effect and water-locking damage in reservoir rocks, causing the decrease of effective permeability to severely restrict productivity; (ii) as the invasion of formation water and another fluid, the locking damage may also occur. Changes of irreducible to movable water are simulated by horizontal endpoint calibration of relative permeability, and the damage to gas flow in the early stage of production is simulated through vertical endpoint calibration. Furthermore, relative-permeability curves at different stages are mobilized in module of Schedule model. Large deviation in pressure matching can be avoided during the middle to late stage of production; and (iii) when the equivalent characterization on the start-up pressure gradient is considered in numerical simulation, the model's coincidence in the process of history matching increases to 85% from 45%, indicating this finding more in line with in-situ conditions. In conclusion, these results may perfect seepage theories and numerical simulation technique in tight sandstone gas reservoirs and are of theoretical and practical significance for the development of similar reservoirs with effect.