In order to effectively improve the oil recovery of low permeability and ultra-low permeability reservoirs in China，the idea of constructing a low interfacial tension anionic Gemini surfactant viscoelastic fluid was proposed，so as to meet the requirements of oil displacement agent to improve sweep efficiency and oil washing efficiency，good injectivity and no chromatographic separation. Based on the research of the influence of the molecular structure of anionic gemini surfactant on its solution viscosity，viscoelasticity and interfacial activity，a GCET viscoelastic fluid was constructed，and its main properties and adaptability to the reservoir environment was evaluated. The results showed that the rheology and interfacial activity of carboxylate gemini surfactant solutions was better than that of sulfonate gemini surfactant solutions；the carboxylate gemini surfactant solution with a large number of carbons in the hydrophobic chain（m=18）and a moderate number of spacers（s=3）had better rheological properties；the carboxylate Gemini surfactant solution with a larger number of carbons in the hydrophobic chain（m=18）and a smaller number of carbons in the spacer group（s=2）had a higher interface activity. Based on this，the GCTE fluid optimized for molecular structure design and construction had good viscosity behavior，viscoelasticity，interfacial activity，and adaptability to reservoir temperature and mineralization. Under simulated mineralization（12000 mg/L），the viscosity of 0.5% GCTE viscoelastic fluid was 12.68 mPa·s；the solution had good viscoelasticity，being of 0.366 <1，relaxation time being of 11.302 s；the steady state oil-water interfacial tension reached up to 2.93 × 10-3 mN/m. The GCTE viscoelastic fluid have a good application prospect in improving oil recovery in unconventional reservoirs.