Compact, portable pulsed power technology is rapidly developed. Solid-state storage medium attracts strong interest, since it has been characterized a high power storage density and good environmental adaptability. In this paper, we use a glass-ceramic substrate, with the dimension of $250~\textrm {mm}\times 95~\textrm {mm}\times 4$ mm, to deliver a high-voltage pulse with a pulse duration longer than 120 ns. In tests, both the pulse duration and the impedance are varying when we are changing the environmental dielectric from the transformer oil or air to the propylene carbonate. A theoretical model is used to analyze the phenomena and verified by the CST simulation. The dispersion analysis shows that a good dispersion characteristic is obtained in the work band of the forming pulse, although the environmental dielectric will influence the pulse duration and characteristic impedance.