This paper studied the temperature dependence of saturation magnetostriction λ4 in both systems Fe80-xCuxSi5B15 and (Fe1-xCox)82Cu0.4Si4.4B13.2. The range of temperature is respectively from room temperature to the Curie temperature of amorphous state and to that of the crystal-line state. The structural changes following the temperature variation are analyzed, and the single-ion microscopic mechanism of magnetostriction is discussed.