A new method of chromate production by applying a new reaction system of KOH-KNO3-H2O (binary submolten salt system) is proposed and proved feasible. Under conditions of temperature 350 degrees C, KOH-to-chromite ore ratio 2:1, stirring speed 700 rpm, KNO3-to-chromite ore ratio 0.8:1, oxygen partial pressure 50%, and gas flow 1 L/min, chromium conversion ratio obtained is >98% with reaction time around 300 min. The decomposition of chromite ore in the system is a typical process of solid-liquid-gas reaction, which is coordinately controlled by mass diffusion in product layer and interface reaction. Apparent activation energy of decomposition in the temperature range from 280 to 370 degrees C is 55.63 kJ/mol. During reaction, oxygen dissolves into KOH-KNO3-H2O melt system first and some cluster, e.g. O-2(2-), is formed and the mass diffusion 2 coefficient of the cluster was calculated. The system can be considered as both a media of oxygen transportation and reactant donator. Potassium nitrate plays a role of catalyst in the oxidation decomposition reaction of chromite ore and potassium hydroxide. (C) 2009 American Institute of Chemical Engineers AIChE J, 55: 2646-2656, 2009