The real time optimization (RIO) of gold cyanidation leaching process has been investigated in this paper. To solve inevitable plant-model mismatch and process disturbance in practice, an RIO strategy based on SCFO (Sufficient Conditions for Feasibility and Optimality) for gold cyanidation leaching process is proposed, where the SCFO are used to enforce the desirable properties (both feasibility and optimality) of the solutions resulted from the traditional RTO methods. The simulation results show that compared with the traditional RTO methods, there is a significant improvement of production cost by enforcing the SCFO under model-parameter uncertainty, model-structure uncertainty and unknown process disturbance, which has laid an important foundation for the successful implementation of the plant-wide optimization and control for hydrometallurgy process. (C) 2015 Elsevier Ltd. All rights reserved.