The formation of histamine in mackerel and other species of fish dring different canditions of storage was studied. The content of histamine in fish was measured colorimetrically by using azo-reagent as colour developer after symples were pretreated with iron exchange resin. The pretreament possesses the advantages of high recovery and easy operation. The experimental results showed that the formation rate of histamine increased with the rise of storage temperature. At 0℃ storage the rate of formation greatly slowed down. based on the temperature of storage and time, the histamine content can be computed. It is therefore applicable to evaluate the guality of fish, and the accidental toxication by histamine might be avoided accordingly..