In order to resolve the fracturing fluid flow-back water treatment problems，the feasibility that the flow-back water of clean fracturing fluid was used as oil displacement agent for enhanced oil recovery was evaluated according to the surfactant fluid flooding technique. The properties of interfacial tension，wettability reversion，adsorption and EOR of the broken fluid of the clean fracturing fluid were studied. The interfacial tension between the broken fluid with mass fraction of 0.001%—0.03% and crude oil was about 10^-3—10^-2 mN/m，and the interfacial tension between the broken fluid with mass fraction of 0.006% and the crude oil was 10^-3 mN/m ultra-low magnitude at the temperature rang from 60 to 90℃. The broken fluid had good emulsifying ability，the water separating proportion of the emulsion，prepared by mixing the broken fluid with mass fraction 0.004%—0.008% and the crude oil at volume ratio of 1∶1，was less than 60%，moreover，the broken fluid possessed good wettability alteration ability，which could change both the oil-wet and water-wet quartz surface to weak water-wet. The enhanced oil recovery was up to 10.04% based on water flooding，when 0.3 PV of 0.006% broken fluid was injected into core in laboratory. The purpose of environment protection and flow-back water reuse were realized，and the oil displacement agent system based on the clean fracturing fluid flow-back water gives a technical support for the further development of low permeability reservoirs.