Nuclear magnetic resonance (NMR) transverse relaxation time (T2) was used to reflect the hydrogen proton component and motility in fermented soybean products in different fermentation time, in order to discover the variation of moisture in fermented soybean products. The T2 signal of fermented soybean was collected by PQ001 analysis software and CPMG sequence to obtain T2 spectrum. The spectrum showes that the hydrogen proton in fermented soybean roughly divided into four phases: T21 (0.01 ~ 1.52 ms), T22 (1.52 ~ 7.05 ms), T23 (7.05 ~ 100 ms) and T24 (> 100 ms). Through the component content analysis, along with the anaerobic fermentation, decomposition of protein-based materials by microbial enzymes, metabolic activity of microorganisms and the formation of flavor substances, the combined water reduced continuously. There was a process of mutual transformation of water in cells (T22 and T23), and the content of free water also decreased in a certain extent. During the fermentation, the umami ingredients increased largely, amino nitrogen improved significantly, flavor substances increased significantly, the color of soften soybean deepened. The nuclear magnetic resonance (NMR) method can indirectly reflect the formation of the flavor and the change in texture during fermentation.