Frame multispectral imaging technology is capable to acquire multi-band spectral images simultaneously, and has been widely used in many fields such as material analysis, environment monitoring and so on. A frame multispectral imaging method based on light field imaging technology is employed, and a secondary imaging system is designed to reimage the multispectral image obtained by the light field imaging system onto the photosensitive surface of detector. It is able to avoid the damage of detector caused by the direct contact between the microlens array and the photosensitive surface, and decrease the difficulty of adjustment and installation for the system as well. In addition, the factors that cause channel spectra aliasing are discussed. Based on the pixel gray matching method, the vector coordinates of each channel points are extracted and the spectral channel information is obtained. Besides, a series of plane calibrations under different light intensities are operated to get the normalized light throughput of every channel for calibrating the gray errors of the system. Eventually, an experimental system is set up, the multi-spectral instantaneous detection to indoor target is realized, and the clear recovered spectral images are obtained.