Bioventing is one of the remediation techniques for volatile organic compound (VOC) contamination with VOC in the vadose zone. The object of this study is to investigate the pollutant transport and removal during aeration treatment focusing on convection, biodegradation, and volatilization. As for the result of 20-cm column experiment, dodecane removal ratio of the samples with aeration was about 20 % higher than those with no aeration. But after 30 days, the increasing rate of dodecane removal ratio decreased drastically in all cases. Total germ density increased after 10 days, but stopped increasing after 30 days. In the samples with higher water content, total germ numbers and dodecane removal ratio increased largely at the inlet of the air. From the estimations of the contribution of volatilization and biodegradation, the authors found that volatilization played a more important role on dodecane removal during the first 10 days of the column experiment, and biodegradation became predominant afterward.