At present, SPASER(Surface Plasmon Amplification by Stimulated Emission of Radiation) is the smallest nanoscale active device, which is the first to function under visible light. In this paper, the MIM(metal-insulator-metal) waveguide structure of a double steady state was designed, which introduces the SPASER technology, namely, the surface plasmon wave amplifier. The amplifier was obtained by deriving from the Bloch equation using the SPASER laser theory. When the pumping rate was less than the threshold value, the number of the gain medium inversion particles remained 0. Otherwise, the number of the inversion particle grew linearly. The geometrical characteristics of the system could be completely described by the eigenmode function. On the central eigenmode, the system property entirely depended on the material parameters. Choosing the appropriate material parameters could make each state of the relaxation characteristic time remain at the level of the picosecond magnitude. The calculated results of the model show that the improved structure does not change the strong localized characteristics of the SPPs(Surface Plasmon Polaritons). The device solves the limitation on the surface plasmon net profit elimination caused by SPASER internal feedback.国家自然科学基金(61361011)；广西自然科学基金(2015GXNSFBA139257)；广西师范大学重点项目(2015ED03)； 广西自动检测技术与仪器重点实验室(YQ16206)