Abstract: Al-12% Si and Zr(CO₃)₂ were selected as reactive components to synthesize Al₂O₃, Al₃Zr particulate reinforced Al12% Si matrix composites. The as-cast samples were got via a rapid solidifying method. The relationship between thermal expansion displacement and temperature in the range of 50 to 500℃ was tested using a thermal expansion instrument and the average linear coefficient of thermal expansion (ALCTE) was also calculated. The results show that the ALCTE decreases with the increase in theoretical volume fraction of particulates (TVFP) at the same temperature. Meanwhile temperature is an important factor to influence the ALCTE. At 50 to 300℃ the ALCTE increases gradually with the increase in temperature, while at 300 to 500℃ it decreases gradually with the increase in temperature, and the value arrives maximum at 300℃. Furthermore the theoretical ALCTE values were calculated with the Rom, Turner and Kerner models individually. The test results of ALCTE are similar to the values from the Turner model. At last it is concluded by analyzing the residual thermal stress at interfaces that the (Al₂O₃ + Al₃Zr)_p/Al-12% Si composite can prevent the materials from plastic deforming at high temperature because of its low thermal expansion.