Thermal fatigue resistance is one of the most important parameters to design engine materials. The thermal fatigue crack growth behavior of alumina short fibre (V-f = 18 vol.%) reinforced AlSi12CuMgNi aluminum alloy composite has been investigated under thermal cycling condition between room temperature and 280 degrees C. Initiation and propagation of thermal fatigue crack have also been discussed. The results show that in the range of short crack, the fibres play an important role in the path of thermal fatigue crack, and the crack propagation rate of composites is much larger than that of the matrix alloy.