Abstract: Alumina sol was synthesized from dissolution of aluminum powder in aluminum chloride hexahydrate solution.The mullite-alumina sol was obtained by mixing alumina sol，silica sol blocking agent，and spinning additive polyvinyl alcohol （PVA）.Effect of addition content of spinning additive on sol spin-abilty was studied.Results showed that viscous sol with spin-ability was obtained and linear or nonlinear molecular chains were produced by reacting between colloidal particles in sol when the sol was concentrated；organic-inorganic hybrid molecular chains were generated and spinning performance of sol was improved by adding spinning assistant when the active groups of Al/Si ions or particles reacted with spinning assistant in sol；the maximum length of the gel fibers achieved about 100 cm when the blocking agent and 1%（mass fraction） spinning additive were added at the same time.The fibers with a smooth surface and uniform diameter were obtained by sintering at 1 200 ℃ for 1 h，and their main phase was identified as γ-Al₂O₃ and mullite.

Key words: long fibers, mullite, alumina, PVA