Abstract: By the sandstone micro-model water flooding experiment of ultra-low permeability sandstone reservoir in the Ordos Basin,the controlling factors for oil displacement efficiency are studied in this paper.It's discovered that the wettability is different,so is the displacement mechanism.There are displacement and denudation mechanism in water wet reservoir,while there are displacement and flow mechanism in oil wet reservoir.There are many factors that affect the oil displacement efficiency such as the property,the pore structure,the injection volume,the injection rate,the wettability,and so on.The water drive development is sensitive to the injection speed in ultra-low permeability sandstone reservoir.For different reservoir,appropriate injection speed should be adopted in order to improve the effect of development.