The surface tension of liquid Ti-Al alloys at 1758 K was determined by the improved sessile drop method. The surface tension of liquid Ti-Al alloys were calculated using the Butler’s model and several modified ideal solution models. Results showed that the surface tension of liquid Ti-Al alloy decreases with increased Al concentration. Experimental results agree well with both the Butler’s model and the modified ideal solution model. The segregation of Al atoms to the surface occurs at all bulk concentrations of Ti-Al alloys. Al with lower surface tension prefers to segregate on the surface of liquid Ti-Al alloy, whereas Ti with higher surface tension prefers to segregate inside the molten alloy. The effect of surface active solute on the surface tension of liquid Ti-Al alloy was also discussed. Sulfur was found to have a larger effect on the surface tension of alloy. The surface tension of liquid Ti-Al alloy decreases with increased sulfur concentration. Sulfur concentration on the surface is higher than in the bulk. Thus, the adsorption of sulfur for Ti-Al alloys is a positive adsorption.