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The effect of ethylene diamine tetraacetic acid ( EDTA) modification on the physico-chemical properties and catalytic performance of silica nanosprings ( NS) supported cobalt ( Co) catalyst was investigated in the conversion of syngas ( H2+ CO) to hydrocarbons by Fischer-Tropsch synthesis ( FTS) . The unmodified Co/NS and modified Co/NS-EDTA catalysts were synthesized via an impregnation method. The prepared Co/NS and Co/NS-EDTA catalysts were characterized before the FTS reaction by BET surface area, X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy ( XPS) , differential thermal analysis ( DTA) and thermogravimetric analysis ( TGA) in order to find correlations between physico-chemical properties of catalysts and catalytic performance. FTS was carried out in a quartz fixed-bed microreactor (H2/CO of 2:1, 230℃ and atmospheric pressure) and the products trapped and analyzed by GC-TCD and GC-MS to determine CO conversion and reaction selectivity. The experimental results indicated that the modified Co/NS-EDTA catalyst displayed a more-dispersed phase of Co3 O4 nanoparticles (10. 9％) and the Co3 O4 average crystallite size was about 12. 4 nm. The EDTA modified catalyst showed relatively higher CO conversion (70. 3％) and selectivity toward C6-18(JP-8, Jet A and diesel) than the Co/NS catalyst (C6-14) (JP-4).