In order to achieve imbibition stimulation of low permeability tight oil reservoirs，a microemulsion additive（ME）for increasing production by imbibition stimulation was developed， based on the integrated construction method of “compression-injection-recapture”and with the goal of improving the performance of fracturing fluids. The major raw ingredients were fatty alcohol alkoxylation sulfate anionic surfactant（SY-1）and methyl 9-octanoate（MS-9）. The phase behavior was explored by fitting a ternary phase diagram，and then the formula was optimized using orthogonal tests. Its performance was evaluated by laboratory experiment，and then the stimulation effect during fracturing was tested. The results showed that the optimum formula for preparing ME was obtained as follows：25% SY-1，12.5% triethylene glycol butyl ether，37.5% KCl aqueous solution（2%mass fraction） and 25% MS-9. The average particle size of the microemulsion was 70.5 nm. It could keep stable under the conditions of long standing（180 days）and high-speed centrifugation（8000 r/min）. It could also reduce the interfacial tension to the order of 10^-4～10^-3 mN/m. Compared with water，it could reduce the contact angle by approximately 35°. It could maintain high interfacial activity after 8 adsorptions with core powders，indicating strong anti-sorption ability. It had good compatibility with fracturing fluid. When the fracturing fluid without ME was used as blank control，ME could enhance the oil washing efficiency by 54.94 percentage points—61.82 percentage points during the simulated fracturing entry stage. During the simulated fracturing well stage，the imbibition displacement impact might be raised by 15.68 percentage points. Meanwhile，during the flowback stage，it could accelerate the speed and degree of crude oil recovery，and then the crude oil recovery rate could be increased by 32.56 percentage points. The microemulsion had the advantages of small particle size，strong stability，low interfacial tension between oil and water，good wetting improvement effect and strong adsorption resistance. It could increase oil recovery during the whole process of fracturing construction. The effect of increasing permeability and oil displacement was remarkable.