A capillary plasma z-pinch as an alternative active medium of soft X-Ray lasers was studied experimentally and theoretically. The theoretical analysis was based on the self consistent solution of the so called “snow plow” model. The dynamics of pinched plasma is determined by the capillary parameters and by the time dependence of electrical current passing through it. The current time dependence is strongly influenced by the electrical circuit connected to the capillary. In order to optimize the pinch dynamics from the point of view of laser pumping, the effects of the electrical circuit parameters on plasma evolution are studied in this paper