The planar solid-state pulse-forming line (planar solid-state PFL) is an important solid-state device used in compact pulse power systems. Moreover, pulsed power systems constitute a crucial element within electroporation systems. In this paper, we present theoretical and simulation analyses of the influence of the ground electrode structure of the planar solid-state PFL on the edge electric field and thermal distribution of high-voltage electrodes and the design of a novel improved solid-state PFL (opposite-electrode PFL) that differs from the classic planar solid-state PFL (full-electrode PFL) in which the ground electrode covers the entire plane. The ground electrode of the opposite-electrode PFL is structured to be consistent with the high-voltage electrode and positioned directly opposite to enhance the withstand voltage capacity of the planar solid-state PFL. The simulation results show that when the ground electrode width is the same as the high-voltage electrode, the electric field strength at the edge of the electrodes is smaller. In the electrostatic field simulation, the edge electric field strength of the high-voltage electrode in the opposite-electrode PFL is smaller than that of the full-electrode PFL, which indicates that the opposite-electrode PFL may have a higher withstand voltage. The experimental results show that the opposite-electrode PFL has a higher withstand voltage than the full-electrode PFL, which verifies the correctness of the theoretical and simulation analyses. Furthermore, the opposite-electrode PFL surface temperature rise showed a better performance after running the same test repeatedly. The findings of this study are conducive to enhancing the maximum output voltage or compactness of pulsed power systems and highlight the additional potential for the utilization of solid-state pulse generators in electroporation systems.