Melt-spinnable polyaluminocarbosilane (PACS) is of importance as the precursor to prepare the Si-C-Al-O ceramic fibers, which can be employed for the preparation of SiC fibers with high tensile strength and good thermal stability. In this work, low-softening-point polycarbosilane (LPCS) was synthesized by pyrolysis of polydimethylsilane and applied to prepare PACS precursors with variable aluminum content by the reaction with aluminum(III) acetylacetonate. GPC, H-1 NMR, UV-Vis, FT-IR, Si-29 NMR, Al-27 MAS NMR, TGA, and elemental analysis were used to analyze the composition and structure of the PACS precursors. Finally, Si-C-Al-O fibers were obtained successfully by melt-spinning, curing, and final pyrolysis of the precursors. The method demonstrated in this work can be further extended to synthesize other melt-spinnable metal-containing polycarbosilane (PMCS, M: Zr, Ti, Fe, Co, et.) of high ceramic yield and adjustable M content by reacting LPCS with other corresponding metal-containing compounds.