Abstract: The structures of the cortical fibers revealed by biochemical technique of de-membrane in Euplotes sp.has been studied by means of scanning electron microscopy.It is observed that:(1)AZM (adoral zone of membranelles) bracket consists of the membranelle brackets ranged in parallel transversally.Each of the membranelle brackets is a rectangular sheet of fibers in which each fiber has a diameter of 40-50 nm.(2) UM (undulating membrane) bracket consists of over sixty strands of fibers in which a portion of fibers are parallel to one another transversally and another portion longitudinally.The two portions of fibers are woven into the shape of a network.(3) There are three layers of fibers,I.e.the longitudinal fibers,the spherule-coiled fibers and the deep fibers.Beneath the pellicle of the FVTC (fronto-ventro-transverse cirri) region,the layer of longitudinal fibers is divided into several sections by longitudinal ditches just lying beneath the pellicle between the cortical shoulders (or,between the shoulder and the lip).(4) There is also a layer of longitudinal fibers beneath the pellicle of dorsal cortex,and there seems to be a layer of spherulecoiled fibers under the layer of longitudinal fibers.The structures of the cortical fibers are evaluated for possible functions of cortex-shaping,support,movement and morphogenesis of ciliary organelles,etc.