In most statistical process control(SPC), control charts are used in which samples are taken and a suitable statistic is determined and plotted. In these control charts, control limits, ,μ±ko, from which a decision is made are mostly μ±3σ and current literature in control charts are mainly concerned with detecting a shift in the mean. Therefore, when σ is increased considerably after a long time, using control limits set at the first time causes a great deal of economic loss. In this paper the solutions to determine new control limits which maximizes the profit per unit produced and reduce σ to economically optimal level for a certain cost when σ is increased due to process deterioration are proposed. By applying new control limits, σ error decreases considerably compared to apply initial control limits when is increased due to process deterioration. Therefore, false alarm investigation cost drops down to the level of initial a error. And also this solution provides useful information regarding replacement of a process when the process is reviewed regularly.