Abstract: Sepiolite was dispersed with an unique fiberization method and was organically modified with quaternary amines.UP/sepiolite composites were prepared by dispersing the modified sepiolite nano-fibers in UP resin and subsequently cross-linked by using methyl ethyl ketone peroxide,cobalt naphthenate and styrene.The dispersion of the composites system were characterized and analyzed by using FT-IR and SEM and the thermal stabilities of the composites were studied by means of DTA.The results indicated that sepiolite nano-fibers were dispersed unanimously in the UP and the heat degradation temperature of nanocomposites was rised.