The capillary discharge soft X-ray laser scheme is a new way for generating small-size, table-top, high-efficient and cost-effective X-ray laser. In order to obtain stable and high laser energy, it is necessary to optimize parameters related with laser output. The configuration of the main-switch directly determines the waveform of the main current which in turn influences laser output. By means of the study of three types of main-switch, it shows that the circuit inductance of the modified ring-small disk main-switch supported by parallel metal bars is feasible to achieve appropriate main current. It is also concluded that the average main current and average laser energy are increase by 4% and 31% respectively than those before modification, while the lasing probability is increaseed by 60% than that of the original ring-large disk main-switch supported by circular metal pipe. Furthermore, under condition of larger and stable laser energy output, the modified main-switch still inherits the high-voltage resistance of ring-small disk main-switch supported by circular metal pipe, and keeps laser beam with narrow pulse width.