Behaviors of octylphenol polyoxyethylene ether sulfonate (OPES) molecules on the oil-water interface were studied through molecular dynamics simulation (MD). The results showed that OPES could weaken tension of the oil-water interface significantly. The interface tension was only 3.85 mN·m-1 at OPES saturation. The sulfonic group in OPES was the main hydrophilic group and had good hydrophilcity. The interface tension declined from 24.63 mN·m-1 to 17.43 mN·m-1 when temperature increased from 318 K to 373 K
indicating the good high temperature resistance of OPES. OPES maintained the stable properties within 1%-5% Na+ concentration with only 4.47 mN·m-1 increase of the interface tension. Therefore
OPES had good salt tolerance and could tolerate higher Na+ concentration than Ca2+.