Abstract: B₄C/Al-Si composites were prepared by hot extrusion process with Al-Si alloy powder and B₄C powder as raw material.Effect of extrusion process on microstructure of the composites was studied.The results show that B₄C particles distribute uniformly in Al-Si matrix,and no particle agglomeration is found under experimental condition（Extrusion temperature: 350℃~500℃;mould angle: 45°,60ånd 90°;holding time: 30min~120min）.B₄C/Al-Si composites become densification when extrusion temperature reaches 450℃,with 60 min holding time.With the increasing of extrusion temperature and holding time,the number of silicon phase decreases while its particle size increases obviously.Mould angle mainly affects the integrity of B₄C particles,and B₄C particle is broken seriously since local strain enhancing with the increas-ing of mould angle.