Abstract: Using Gleeble-1500 thermal simulator, isothermal compression experiments were carried out on 25vol%SiC_p/Al-30Si composites prepared by vacuum hot pressing under deformation parameters of 420-540℃ and strain rate of 0.003-0.100 s^-1. A constitutive equation including Arrhenius term based on peak stress and considering the effects of strain, strain rate and temperature was established, and the microstructure of composites before and after compression deformation was observed. The results show that the flow stress of 25vol%SiC_p/Al-30Si composites decreases with the increase of deformation temperature and increases with the increase of strain rate, showing a strong sensitivity to deformation temperature and strain rate. The strain exponent (n) and deformation activation energy (Q) of the composite are calculated by linear regression analysis.The thermal compression flow stress of the composite can be described by the hyperbolic sine relationship containing the Zener Hollomon parameters. Pseudoplastic deformation occurs in the composite during low temperature hot compression deformation.Hot working at a temperature of not less than 540℃ and a strain rate of 0.003-0.010 s^-1 can repair and improve the uneven distribution of voids and particles in the composite.