The IFT has been investigated for an interfacially reactive immiscible system composed of oil and water. Ring tensiometry was employed to measure the IFT between the two phases. The results show that the IFT decreases at a linear rate with respect to temperature and the binomial equation can express the reducing trend of the IFT with contact time. The oil-water IFT presents a reduction at both high and low pH. The IFT of diesel engine oil-water and diesel oil-water reach lowest values under acidic and alkaline condition respectively. The IFT of diesel oil-water decreases by 19.2% and the IFT of diesel engine oil-water descends by 11.2% when the concentration of calcium chloride in aqueous solution is 0.2mol/L.