Based on two kinds of SiC particles with the median particle size of 76 μm and 14 μm， six SiC particle grading schemes are designed according to different proportions， and the SiC_P/2024Al composites with 55% volume fraction are prepared by hot isostatic pressing sintering， and then two kinds of stabilization heat treatment strategies， which are “thermal-cold cycle” and “solid solution + thermal-cold cycle”， are designe. The effects of particle grading and heat treatment on the microstructure and dimensional stability of 55%SiC_P/2024Al composites are studied. The results show that the particle grading has a significant effect on the content of Al₂Cu phases in the aluminum alloy matrix. When the proportion of small SiC particles is 40%， it is conducive to the precipitation of Al₂Cu phases. The solid solution + thermal-cold cycle stabilization heat treatment improves the size and distribution uniformity of Al₂Cu phases and the phase stability. In the real and standard models， the thermal mismatch stress level generated by the stabilization heat treatment process shows a trend of first increasing and then decreasing with the increase of the proportion of fine SiC particles. Furthermore， the Mises stress reaches the maximum value （7.95 MPa and 3.52 MPa， respectively） when the proportion is 40%， which is conducive to releasing of the residual stress in the composites and improving the stability of the stress state. After adopting the particle grading scheme of small particle SiC accounting for 40% and carrying out the stabilization heat treatment of “solid solution + thermal-cold cycle”， 55%SiC_P/2024Al composite has the best dimensional stability， with dimensional change rate remaining within ±0.07% for 5 cycles thermal load at 180 ℃.