Abstract: It is found that sodium m-nitrobenzene sulfonate (MS) as an additive can enhance the leaching rate of gold by changing the cathode reaction mechanism without destroying cyanide in leaching solution. The leaching kinetics is studied. The effects of the concentrations of cyanide and the additive, temperature, agitation rate and ore granule size on the leaching reaction are discussed. The Shrinking Core Model can be applied to describe the leaching process. It is concluded that the whole process is controlled by the diffusion of the reactants. An empirical equation for the leaching rate correlation is established. A similating test has been carried out using pyrite cinder in a cascade pond leaching set-up. Experimental results show that MS additive in small amounts can enhance the gold leaching rate, especially in case of low grade gold ores.