A composite fiber saggar used for synthesis of a lithium ion battery cathode material and a preparing method thereof are disclosed. A matrix-enhanced composite fiber saggar material includes mullite,fibrous mullite, cordierite, magnesium aluminate spinel, fibrous alumina, fibrous magnesium oxide, zirconite, ceric oxide, and zirconia-yttrium oxide fibers. A synthetic process is simple, a sinteringprocess is easily controllable, and a prepared material is good in uniformity. The saggar has obviously improved resistance to high temperature and to corrosion than traditional saggars, obviously improved times of repetition and product quality, prolonged service lifetime and excellent thermal shock resistance. A surface layer of the saggar is effectively protected from stripping. The saggar facilitates production cost reduction of the lithium ion battery cathode material, thus increasing economic benefit.