This peper deals with the change in the water activity of saltedfish and the relationship between the Aw and other parameters. Silvery pomfret hasbeen selected as the rew material in the experiment. A combined salting method forfish was accepted at the different duration of salting time, and the changes of wateractivity and salt content were observed, relationship between above mentionedparameters was studied futhermore. The experiments indicated that the decrease inwater activity and water content, and the increase of salt in fish were most rapidat 18 hours from the beginning of salting process afterwards, the change sloweddown. The change basically tended to balance at 34 hours after salting. The experi-ment showed that the linear relationship existed between the water activity, saltcontent and water content. According to this linear relationship, it is possible tocalculate the value of water activity by measuring the content of water and salt. Forthe purpose of controlling fish quality, it can be obtained through the calculation ofwater activity. This method is valuable in improving the effect of preservation of fish.