The traditional manufacturing of short fiber reinforced composites by liquid processes require preform manufacturing using inorganic binders. However, conventional preform manufacturing techniques using inorganic binder are nontrivial procedures requiring high-energy inputs for binder sintering process. A novel alternative fabrication process without preform manufacturing was developed for carbon short fiber (CSF) reinforced Al based composite by low-pressure infiltration method. The volume fraction of CSFs in the composites was 10 vol%. Two kinds of CSF/A1070 composites were compared in this paper, one is manufactured with preform manufacturing technique (with SiO 2 binder) and the other is fabricated without preform manufacturing. The microstructures of both the specimens were observed for defects in the composite. In the CSF/A1070 composite obtained from the new manufacturing process, defects by aggregation of CFSs were reduced. Furthermore, compared with the CSF/A1070 composite by preform manufacturing with SiO 2 binder, the relative density of the CSF/A1070 composite obtained from the new manufacturing process is also observed to increase from 96.6% to 97.8%. CSFs were randomly dispersed inside the composites obtained through the new manufacturing process. The Vickers hardness of the CSF/A1070 composite obtained through preform manufacturing and the new manufacturing process was 33.5 Hv and 41.3 Hv, respectively. Furthermore, CSF/Al based composites using the A356 and A336 alloy as matrix were also manufactured through the new fabrication method. The Vickers hardness, relative density of CSF/A356 and CSF/A336 alloy