Sorption isotherm curve of freeze dried (FD) product was investigated at 20oC, 30oC, and 40oC. Experimental data obtained were verified by eight mathematical models including BET, Bradley, GAB, Halsey, Henderson, Kühn, Mizrahi, and Oswin. Eight models agreed well with experimental data (R2= 0.9374-1,0000) when water activity (Aw) varied from 0.12 to 0.43. However, when Aw is extended ranging from 0.12 to 0.93, only four models named as GAB, Kühn, Halsey and Oswin still show a good agreement with the experimental data. These models can be used in predicting water absorption of FD salmon product at 20oC, 30oC, and 40oC withacorrelation coefficient (R2) ranged from 0.9776-0.9917, 0.9867-0.9991, 0.9821-0.9920 and 0.9464-0.9995, respectively. Errors between experimental and calculated data from the four models were 5.1%, 4.9%, 8.7% and 9.4%, respectively. Water monolayer value is determined at approximately 5%.