Abstract: For the purpose of reuse of dye waste water,a new method is introduced in this paper,in which first use orthogonal experiments to confirm that the main factor influencing the conductivity of dye waste water is the concentration of sodium sulfate.And then,a model of sodium sulfate concentration-conductivity is developed based on the least-square curve fitting of the experiment data,and Fibonacci optimum selection algorithm is used to optimize the obtained model.Finally,the residual quantity of sodium sulfate in the dye waste water can be estimated more accurately by this new method.