A multispectral microscopy imaging system is developed for the single-particle scattering spectroscopy of many individual plasmonic nanostructures simultaneously. The system dispenses with the need for the mechanical scanning of sample stage and thus enables high-speed plasmon resonance imaging of nanostructure arrays. The darkfield scattering intensity images of nanoplasmonic structures at individual wavelengths are acquired with a spectral resolution of 2 nm in the wavelength range from 500 nm to 800 nm, and a frame rate of 2 seconds/wavelength. The images are processed afterwards and the plasmon resonance wavelength of every nanostructure within the field of view can be obtained at once. The plasmon resonance wavelengths of more than 1000 Au colloidal nanoparticles and a nanofabricated Au nanowire array are measured within 5 minutes. The presented high-speed spectral imaging system promises the practical application of large-scale high-density nanoplasmonic sensor arrays for label-free biomolecular detections in the near future.