Abstract: Up to now, the researches on water-using network synthesis have mainly focused on minimizing freshwater consumption with the fixed condition of the water-using processes, ignoring the variability of the processes. To take the alterations into account, a method of matching water-using network design with variable condition was presented. The water currents were classified into fresh, low-contaminant and high-contaminant, then were matched to the processes by considering the inlet limit conditions of the processes. The ratio of the actual and inlet limit flowrates should approach 1, and the processes should be ordered by the outlet limit contaminant concentration from low to high. The computing unit of the method is each process, so the alterations of the conditions can be considered by amending certain parameters, such as flowrate and contaminant concentration. On-line optimization and financial cost control can be made too. Finally, the advantage and effectiveness of the optimization method proposed were shown via a practical example.