In this paper, optimization of a system of square cascades for separation of middle isotopes is introduced, and the optimal square cascade for use in this system is presented. In this case, 130Xe which is a middle isotope, is presented as an example. The separation of this isotope is much more complex than that of other isotopes. The Grey Wolf Algorithm is applied for the optimization, and the parameters of cascade feed flow rate, cut of the cascade, feed location, feed flow of gas centrifuges (GC), and the cut of the first stage are optimized in such a way that the maximum recovery of the target isotope and the maximum cascade capacity are obtained. The optimization results showed that for the nine selected cascades with 180 GCs, the more stages the cascade has, the less number of separation steps are required and the recovery factor and the amount of product increase.