Cometabolic air sparging (CAS) is a new and innovative technology that uses air sparging principles but attempts to optimize in situ contaminant degradation by adding a growth substrate to saturated zone. CAS relies on the degradation of the primary growth substrate and cometabolic substrate transformation in the saturated zone and in the vadose zone for volatilized contaminants. In this study, we have investigated to determine MTBE degradation pattern and microbial activity variation if using propane as a primary substrate at the condition of considering air injection rate and air injection pattern. Laboratory-scale two-dimentional aquifer physical model studies were used and the experimental results were represented that the optimal conditions were as air injection rate of 1,000 mL/min and pulsed air injection pattern (15 min on/off). Over 1,000 mL/min air injection rate and continuous air injection pattern was no affected to increase DO concentration. On the other hand, Injection of propane and propane-utilizing bacteria degraded MTBE partially. And also, injection of propane- and MTBE-utilizing bacteria effectively degraded MTBE and TBA production was observed.