Abstract: The frozen freshwater surimi(salmon)was used as the research object to optimize the optimal conditions of microwave gelation and puffing of the surimi,and the water migration characteristics of the surimi during the microwave gelation and puffing process were studied. The two-factor quadratic regression orthogonal rotation combination design was used to optimize the microwave power and microwave time of the surimi during the microwave gelation and puffing process,,and the changes of water state were studied by low field nuclear magnetic resonance technology. The results showed that the optimum conditions for microwave gelation of surimi were microwave power of 124 W and microwave time of 11.0 min,and the optimal conditions for microwave puffing were microwave power of 273 W and microwave time of 10.0 min.Under these conditions,the golden-yellow fish-flavored brittle expanded surimi product were obtained. The expansion rate of the microwave puffed surimi product was 258%±23.9%,the hardness was(26.98±1.85) N,and the brittleness was(13.95±1.23) N. During the microwave gel process,the state of moisture changeed from a single non-flowable water(T₂₂)to a free water(T₂₃)and a non-flowable water(T₂₂). The T₂₂part was converted to T₂₃. T₂₃ was locked in surimi gel network structure,the stability of water state was enhanced,and the relaxation time decreased. During the microwave expansion process of the surimi,the proportion of each water in the state of water is changed from combined water(1.62%),non-flowable water(95.75%),free water(2.58%)to bound water(88.95%),and non-flowable water(11.05%).