Using glass fiber scraps as matrix and highly dispersed cellulose as enhancer, composite separators are prepared by a simple slurry sieving process. The effects of different composite proportions on the microstructure, mechanical properties, ionic conductivity and electrochemical properties are studied by SEM, tensile test, AC impedance and charge-discharge test, etc. As mass composite ratio is 1:1, the thickness of composite separator is 73.9 um, tensile strength is 29.5 Mpa and ion conductivity is 0.45 × 10⁻³ S cm⁻¹, respectively. Sodium-ion half-cell (Na_xNi[Fe(CN)₆] as cathode) assembled by above composite separator exhibits excellent cycle stability (93.3% of capacity retention after 500 cycles at 1 C), rate capability (85.1% of capacity retention at 10 C) and maintains fine interfacial stability. Compared with glass fiber separator, some performance indicators of this new composite separator have been greatly improved, suggesting its potential application prospects in sodium-ion batteries.