Isomerization oil becomes an important motor gasoline blending component due to increased statutory reduction of aromatics and olefins (high octane number components) contents in motor gasoline. The ionic liquid Et3NHCl-AlCl3 (mole fraction of AlCl3 is 0.67) shows good catalytic performance for the isomerization of n-pentane. The conversion of n-pentane increases with the enhancement of reaction temperature, reaction time. and catalyst/oil volume ratio (C/O ratio), while the yield of isomerization oil and the selectivity of isoparaffins decrease. The optimal reaction temperature, reaction time, and C/O ratio are 30 degrees C, 3 h, and 1:1, respectively. Under the optimal reaction conditions, the conversion of n-pentane, the yield of isomerization oil, and the selectivity of isoparaffins are 44.61 wt %, 96.07 wt %. and 90.52%, respectively. High conversion of n-pentane favors the octane number improvement of isomerization oil without the circulation of n-pentane, while low conversion of n-pentane is preferential with the circulation of n-pentane.