A series of Fe3O4 catalysts supported on chitosan (CTS) were prepared through successive hydrothermal synthesis, cross‐linking, and mechanical mixing of CTS. The prepared catalysts were characterized by SEM, XRD, N2 adsorption‐desorption, XPS, FT−IR, TG, H2−TPR, CO−TPD, C3H6−TPD, and contact angle (CA) analysis, then evaluated for their performance in the Fischer‐Tropsch synthesis (FTS). CTS supported Fe3O4 catalyst increased the hydrophilicity of the pristine un‐supported Fe3O4. Results revealed that the catalysts exhibit high activity with tuned product distribution in FTS. The water gas shift reaction is facilitated over the Fe3O4/CTS catalysts, and their selectivity for light olefins is significantly improved by inhibiting the secondary reaction of the initial olefins, which was confirmed by C3H6−TPD experiments. The Fe3O4 particle size has a significant influence on product distribution, with larger Fe3O4 particles being beneficial to the formation of light olefins. The 30 % Fe3O4/CTS catalyst has light olefin selectivity of 35 % with an O/P value of 2.19, which are higher than those of 21 % and 0.62 over the pristine Fe3O4. [ABSTRACT FROM AUTHOR]