Abstract: The mathematical models for secondary dendrite arm isothermal coaening kinetics are developed for multicomponent. alloys on the basis of four physical models previously proposed. Calculations based on these models show qualitive agreement with experiment conducted by Nobuy-uki Moriet on Al-Cu-Si, Al-Cu-Fe and Al-Cu-Mn alloys. It shows that the increasing of solute contents favors the thinning of secondary dendrite arms under the condition that the local solidification times are kept constant for multicomponent alloys during solidification processing.