In this study, a multi-channel analysis device based on localized surface plasmon resonance (LSPR) is demonstrated. This device comprises a broadband light source, a multi-channel precision alignment system, and a fiber spectrometer. The Savitzkky-Golay algorithm is used to process the original spectral data, and fitting curves are obtained. Further, the LSPR wavelength responses of spherical gold nanoparticles (AuNPs) with diameters of 5.0, 13.5, 25.5, and 41.0 nm in the surrounding mediums with different refractive indices are studied. The experimental results demonstrate that the LSPR peak wavelength is positively correlated with the particle size for the same refractive index, and the resonant wavelength is closely related to the refractive index of the surrounding medium. The sensitivities of the refractive index are 59.46 and 70.38 nm/RIU (refractive index unit, RIU) for AuNPs with diameters of 25.5 and 41.0 nm, respectively. The proposed device does not require any tediously long wavelength scanning procedures owing to the combination of a multi-channel alignment system and a fiber spectrometer, thereby providing an inexpensive and rapid optical detection system for conducting LSPR research.