An improved metal-insulator-metal(MIM) waveguide structure was used to realize the potential of surface plasmon amplification by stimulated emission of radiation(SPASER) as amplification, although a major problem is that the net gain of SPASER equals zero, which makes it unsuitable for amplification. With the use of a theoretical Hamiltonian model as basis, the lasing conditions were obtained. The numerical calculations of these conditions show that overcoming the inherent feedback and eliminating the surface plasmon(SP) net gain are feasible by using the improved MIM waveguide structure, which can achieve stable SP excitons in less than 100 fs. This study shows that the improved SPASER amplifies with a response time of 100 fs, a bandwidth of 1.5-2.0 THz, and an SP gain of 30-60 dB. SPASER amplifier research provides theoretical and technological foundation for large-scale integrated photonic chips.