An intermediate decyl naphthalene (DN) was synthesized by Lewis acidic ionic liquid catalyzed Friedel-Crafts alkylation reaction from naphthalene and α-decene, and the structure of DN was identified by FT-IR and 1H NMR. Decylnaphthalene sulfonates (DNS), the anionic flooding surfactants with identified structure,tunable composition and Krafft point below 0 ℃ were synthesized from DN following by sulfonation and neutralization, and the compositions of DNS were determined by HPLC-MS. The interfacial tensions of aqueous DNS solutions against normal paraffin simulated oil phases were measured. The experimental results showed that products DNS1-1 and DNS3 could decrease the O/W interfacial tensions to 10-3 mN/m within the lower surfactant concentrations of 0.25 wt.%~0.4 wt.% and played good salt tolerance simultaneously. It was noted that the composition stability and the phenomena of composition-dependent ultralow interfacial tensions were reproducible for different batches of DNS1-1.