Momentum correction coefficient (K) is an important parameter for the mixing process of two jet flows. in this paper, momentum correction coefficient for two jet flows mixing in a tee junction was investigated with systems of air-air, water-water and air-water in a wide region of mass ratio of flow rate. The pressure drop was analyzed, where the total pressure drop was mainly attributed to momentum exchange and friction. Based on the experimental data, pressure drop due to momentum exchange was obtained by extrapolation methods, and then the momentum correction coefficient was fitted. it turned out that the momentum correction coefficient was mainly dependent on the momentum flux ratio (M) of the two jets and almost independent with the physical properties of jet flows. The relationship between K and M was correlated as the following equation: K = 1 + 0.256M(0.223) (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.