In this paper, multi-plasmon resonances in microstructured optical fibers (MOFs) are proposed and analyzed as a methodology to achieve surface-plasmon-resonance (SPR) sensors with a wide refractive index (RI) detection range and as a multi-analyte sensing technique. For this purpose, the influence of multi-plasmon excitations on the performance of SRP sensors based on suspended core microstructured optical fibers (SCFs) with three and four holes was studied theoretically. A large analyte RI range from 1.33 to 1.39 was evaluated to investigate the sensing performance of the SCF-based SPR sensors. The results indicate that the excitation of higher order SPP modes could be an alternative to achieve SPR sensors with a wide analyte RI range and competitive resolution. We found that the shape of the fiber core and the metallized surface have a significant effect on the plasmonic excitation spectra. We also found that multi-plasmon excitations have potential for multi-analyte sensing and self-reference. This paper can provide a reference for developing MOF-based SPR sensors.