In order to improve the oil recovery of low permeability reservoir，active water imbibition huff and puff technology is widely used in horizontal wells after fracturing，and the key to its success is to develop a high-efficiency imbibition agent formula. In this paper，a low interfacial tension anion-nonionic surfactant，tristyryl polyoxyethylene ether sodium hydroxypropyl sulfonate （TPHS）was developed by "one pot boiling". The interfacial tension and salt resistance performance of HPHS was investigated. A low interfacial tension nano fluid，composed of TPHS，AOS and nano- SiO2 particles，was optimized by contact angle test， spontaneous infiltration test and forced infiltration test，and the displacement evaluation was carried out. The results showed that the interface tension between TPHS solution and the crude oil could still be kept at 10- 1 mN/m at the temperature of 80℃ and at the salinity of 300 g/L，exhibiting good salt and temperature resistance. The interface tension between the complex system of 0.1% TPHS+0.2% AOS and the crude oil decreased to 10-2 mN/m，which was helpful to displace crude oil in small pores. The addition of a small amount of nano- SiO2 particles（0.05%）could produce synergistic effect of wetting with TPHS and AOS，which could improve the imbibition rate and enhance the recovery rate by 12.7%，compared to that of the surfactant flooding. At the same time， the emulsion stabilized oil wall could be formed and the anhydrous oil recovery period could be prolonged. It was confirmed that the addition of nano-SiO2 to surfactant mixtures resulted in enhanced imbibition oil recovery in low permeability reservoirs.