The thermal expansion behaviors of aluminum matrix composites reinforced by SnO2-coated Al18B4O33 whisker were investigated. The experimental results indicate that the SnO2 coating of whisker can reduce the coefficients of thermal expansion of the composite both in transverse direction and longitudinal direction, and the lowest coefficients of thermal expansion can be obtained in the composite with suitable whisker coating. A model was proposed to clarify the relationship between the coefficients of thermal expansion of the composites and change of thermal mismatch stress in the matrix of the composites with different whisker coating contents. Significant impact of SnO2 coating content on variations of thermal mismatch stress is confirmed. (C) 2013 Elsevier B.V. All rights reserved.