Magnesium borate whisker-reinforced aluminum matrix composite is a new aluminum matrix composite with high properties and low cost. In the study, the residual stress changing behaviors on heating and cooling of the composite were investigated through the coefficient of thermal expansion (CTE) curves. On heating, the tensile stress relaxation and compressive stress generation in the matrix of the composite results in the CTE of composite is smaller than that predicted by mixture rule, but the compressive stress relaxation in the matrix of composite causes the CTE of composite is larger than that predicted by mixture rule. The tensile and compressive stress changing rates with temperature are linear on heating in the matrix of the composite at lower and higher temperature ranges. The CTE of the composite on cooling is smaller than that on heating. (C) 2007 Elsevier B.V. All rights reserved.