The present invention relates to a real-time detection device for municipal solid waste components in an incinerator. The real-time detection device includes: an optical fiber sensor, which faces combustion flame of municipal solid waste combustion region through an observation hole in the incinerator; a spectrometer, which is used for receiving optical signal of the optical fiber sensor; an industrial personal computer, which is used for receiving data of the spectrometer and outputting the municipal solid waste components according to a municipal solid waste component detection program; the municipal solid waste component detection program obtains combustion flame spectral information of municipal solid waste in the incinerator by utilizing the optical fiber sensor and the spectrometer, and detects the municipal solid waste components in real time based on combustion flame spectrum of a single waste component. The present invention further relates to a real-time detection method for municipal solid waste components in an incinerator. Compared with manual classified sampling and detection, the device and method provided by the present invention have the advantages of high efficiency, rapidness, accuracy, capability of being updated in real time; and can realize stable combustion of the municipal solid waste in the incinerator, and reduce emission of pollutants and realize efficient and clean utilization of the municipal solid waste.