The change of carbon in marine sediment is the information bridge between the past and the future of the marine ecosystem, which reveals the law of the marine ecological process. Therefore, the research on the carbon content of marine sediments plays an important role in mastering the carbon cycle law of the marine ecosystems, studying the global carbon cycle, and studying the response and feedback to climate change. Spectrum technology is a fast and non-destructive measurement method, which has been widely used in quantitative analysis. Multispectral fusion based on spectral technology, through the combination of multiple spectral data, we can get more information than a single spectrum, which is conducive to the analysis of substances. In this paper, multispectral fusion was applied to the study of carbon content in marine sediments. 161 samples of Qingdao, China intertidal sediments are taken as samples. The visible near infrared spectra of sediments were collected by QE65000 spectrometer (spectrometer 1) and AVANTES optical fiber spectrometer (AvaSpec-ULS2048) (spectrometer 2), respectively. The spectra of the two spectrometers were fused, PLSR and BPNN were used to establish the carbon content model. The results of PLSR modeling showed that the results of multi fusion spectrum were better than that of spectrometer 2, slightly lower than that of spectrometer 1, and the RPD value was 1.968. The results of BPNN modeling showed that the results of multi fusion spectrum were better than those of two single spectrometers, and the RPD value was 2.235. The spectra after multispectral fusion were divided into several bands to find the characteristic bands of carbon in sediments. By analyzing the results of the multispectral fusion model, 560~790 nm was the best, the RC2 was 0.949, the RMSEC was 0.550, the RP2 was 0.874, the RMSEP was 0.733, and the RPD was 2.823. Compared with spectrometer 1, spectrometer 2 and multispectral fusion, the prediction effect was significantly improved. Therefore, using the multi fusion spectral characteristic band to establish the model of the carbon content of marine sediments can improve the prediction results of the carbon content in marine sediments. It can establish a more accurate model of the organic carbon content of sediments, which will lay a foundation for the rapid determination of the organic carbon content of sediments.