Introduction: Nonlinear C8 hydrocarbons, like iso-octane, can raise the octane rating of gasoline due to its better anti-knock characteristics, allowing the use of higher compress ion ratios and higher thermal efficiencies. The benefits of nonlinear C8 addition to gasoline have always been recognized for practical reasons. Fischer-Tropsch process and isomerization reaction have been explored to produce nonlinear C8 hydrocarbons by using different types of catalysts such as classical zeolites, metal oxides for commercially applied process. Olefin oligomerization on these catalysts has also been reported to harvest nonlinear C8 hydrocarbons. However, the reaction temperature above 100 oC is relatively high, demanding high energy-consumption. Metal-organic Frameworks (MOFs) with coordinated unsaturated sites (CUSs) on late-transition metals have often been researched as desiccant and adsorbent, and are reported being tested in gas-phase olefin dimerization, indicating the MOF materials take the potential value in the application of oligomerization. Herein, highly selective ethylene tetramerization is observed on a Metal-Organic Framework, MIL-100(Fe) under mild conditions to obtain nonlinear C8 hydrocarbons. Methodology: MIL-100(Fe) was synthesized and vacuum treated at different temperatures to obtain MIL-100(Fe) catalysts with CUSs. Then the treated MIL-100(Fe) catalysts were utilized in ethylene slurry oligomerization. Results: All the MIL-100(Fe) catalysts show high selective tetramerization activities. Specifically, the catalytic activity of the catalyst treated under 250 oC reaches over 1.27×105 g/(molFe.h) and the selectivity for C8 is more than 70% under 10 atm at ambient temperature. There is almost 90% nonlinear C8 tetramers components in the obtained tetramers. Conclusion: The operation of ethylene tetramerization on MIL-100(Fe) is more easily realized at mild conditions, which is an energy-efficient procedure. And the tetramers products containing nonlinear C8 components are suitable as the addition to gasoline to increase the octane number.