The conductivity of the solid electrolyte based on urea and thiourea has reached 6. 84 × 10-3 S. cm-1 at room temperature. Analysing the conductive process of this electrolyte we found that thiourea changes into ammonium thiocyanate at a high temperature, which ionizes into ions, and can conduct the current. We obtained a red color substance through electrolysing the SPE. Analysing it with IR, UV and FAB, we confirmed that it is a polymer with a structure (SCN)n. It is proved that the aninon is SCN-. When weadded HCl into the acetone solution of the SPE, it was found that white precipitation material appeared in the solution, which was identified as NH4Cl, so the canon is NH4+.