In order to study the effect of composite preservatives (chitosan, tea polyphenols and lemon juice) on the quality of rainbow trout fillets during storage, The fresh-keeping effects were listed as follows: texture, pH, TBA, TVB-N and the total number of colonies. LF-NMR and electronic nose technology were used to explore the changes of moisture content and volatile components during the storage. The results showed that the composite preservative group could better maintain the texture characteristics of fillets compared with the control group, and at the same time, it also could delay the TBA value, TVB-N value and total viable counts change of fillets. The T₂₁ amplitude of the two groups decreased gradually during the storage with the low field nuclear magnetic resonance(LF-NMR) measuring. In the late storage period (12~14 d), the proportion of free water in the treated group was significantly lower than the control group (P<0.05). Comparing with the initial period, the proportion of free water of two groups increased. Both principal component analysis(PCA) and linear discriminant analysis(LDA) could better distinguish the quality of fish fillets during storage. Loading analysis(LA) showed that the components that caused the bad freshness of fish fillets were mainly nitrogen oxides, inorganic sulfides, aromatic components, ethanol and so on. The results of PCA indicated that the control group began to spoilage on the 6th day, while the treated group began to spoilage on the 10th day. In summary, the results of LF-NMR and electronic nose were consistent with the results of physical and chemical indicators.