Polyaluminocarbosilane(PACS) was synthesized by reaction of polysilocarbonsilane(PSCS)with Al- (AcAc)3

(AcAc：acetylacetonate)at normal pressure and high temperature

then PACS fibers were prepared through melt spinning of PACS．The composition and structure of PACS fibers were examined by measurements of element analysis

GPC

XPs

IR

29Si-Solid NMR and27Al一Solid NMR；the properties of PACS fibers were studied by TG

IR

weight gain and SEM．PACS synthesiznd through the reaction of AI(AcAc)3 with PSCS by mass ratio of 6：100 was best fitting for preparing PACS fibers．Its empirical formula was SiC2.0 H7.5O0.13Al0.018 and the molecular weight was about l700．The chemical structure unit included SiC4

SiC3H etc

and si—O—A1 bonds also existed in the PACS fibers．Under nitrogen atmosphere

the ceramic yield of PACS fibers was about 52％；during the curing process of PACS fibers in air．the Si--H bond reacted with oxygen

and Si—O—Si bond was formed．The ceramic yield of cured PACS fibers was about 80％ and the properties of SiC(OA1)and SiC(A1)ceramic fibers were excellent．It was proved that PACS fibers were very fitting for making SiC(OA1) and SiC(A1)ceramic fibers．