Direct wax synthesis from syngas was implemented by supercritical-phase Fischer-Tropsch synthesis (FTS) reaction. By introducing supercritical-phase n-pentane into the reaction, waxy hydrocarbon formation rate was increased significantly while tight hydrocarbon formation rate was suppressed effectively. Anti-Anderson-Schultz-Flory distribution of FTS hydrocarbons was realized at lower temperatures, such as 473 K. The intermediate, olefins, readily readsorbed onto the catalyst surface and significantly stimulated the carbon chain-growth process.